Colon and rectal cancers

Health Topics A-Z

Health Topics A-Z

Colon and rectal cancers

Highlights

Drug Approval

In September 2006, the Food and Drug Administration approved panitumumab (Vectibix) for the treatment of patients with colorectal cancer that has spread to other parts of the body following chemotherapy. Like cetuximab (Ertibux), panitumumab targets the epidermal growth factor receptor (EGFR) on cancer cells. Panitumumab is the first new colorectal cancer drug approved since 2004. The FDA granted accelerated approval to panitumumab based on a clinical trial of patients with metastatic cancer. The average time to disease progression or death was 96 days in patients treated with panitumumab compared to 60 days in patients who received standard care.

Diet and Colorectal Cancer Recurrence

Evidence indicates that diet plays a role in colorectal cancer prevention. Now, a 2007 study in the Journal of the American Medical Association (JAMA) suggests that dietary factors also affect the risk of cancer recurrence. Patients with stage III colorectal cancer who ate lots of red meat, refined grains, and sweets had a higher risk of cancer recurrence and death than patients whose diets were high in fruits and vegetables, poultry, and fish.

Folic Acid No Good for Prevention?

Many experts have long believed that folic acid supplements may help protect against colorectal cancer. But according to a 2007 JAMA study, high-dose folic acid supplements may not prevent colorectal cancer and may actually increase the risk for adenomatous polyp formation. Adenomatous polyps are benign colorectal tumors that can potentially become cancerous. In the study, patients who took folic acid supplements had a greater risk of developing new, more numerous, and larger adenomatous polyps than patients who did not take the supplements.

NSAIDS Not Recommended for Colorectal Cancer Prevention

In March 2007, the U.S. Preventive Services Task Force (USPSTF) recommended against the routine use of aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) to prevent colorectal cancer in people who are at average risk for this disease. Several recent studies have indicated that aspirin, and NSAIDs such as celecoxib (Celebrex), can help prevent colorectal cancer. But the USPSTF notes that the risks of these drugs outweigh the benefits. Long-term daily use of NSAIDs increases the risk for gastrointestinal bleeding, kidney function problems, and heart attack and stroke.

Introduction

Cancers of the colon and rectum, often referred to collectively as colorectal cancer, are life-threatening tumors that develop in the large intestine.

More than 80% of colorectal tumors evolve from adenomatous polyps. These gland-like growths develop on the mucous membrane that lines the large intestine. They are usually either:

Tubular polyps, which protrude mushroom-like
Villous adenomas, which are flat and spreading and are more apt to become malignant (cancerous)

Polyps are very common and almost always benign. Their numbers increase with age. Polyps are found in about 25% of people by age 50, and 50% of people by age 75. Fewer than 1% of polyps under 1 centimeter (slightly less than half an inch) become cancerous. About 10% of larger polyps become cancerous within 10 years, and about 25% of these larger polyps become cancerous after 20 years. Certain inherited polyps can become cancerous more rapidly.

The Gastrointestinal Tract

Digestion takes place in the gastrointestinal (GI) tract, essentially a long tube that extends from the mouth to the anus. It is a complex organ system that first carries food from the mouth down the esophagus to the stomach. Food then travels through the small and large intestines before being excreted through the rectum and out the anus.

The esophagus, stomach, large and small intestine -- aided by the liver, gallbladder, and pancreas -- convert the nutritive components of food into energy and break down the non-nutritive components into waste to be excreted.

Esophagus

The esophagus is a narrow muscular tube, about 9 1/2 inches long that begins below the tongue and ends at the stomach.

Stomach

In the stomach, acids and stomach motion break food down into particles small enough so that the small intestine can absorb nutrients.

Click the icon to see an image of stomach anatomy.

Small Intestine

The small intestine, despite its name, is the longest part of the gastrointestinal tract, extending for about 20 feet. Food passes from the stomach through its three parts: first the duodenum, then the jejunum, and finally the ileum. Most of the digestive process occurs in the small intestine.

Click the icon to see an image of small intestine anatomy.

Large Intestine

Undigested material, such as plant fiber, is passed next to the large intestine, mostly in liquid form. The large intestine is wider than the small intestine but only about 6 feet long. It is the final portion of the digestive tract and includes the cecum, the appendix, the colon, and the rectum, which extends to the anus.

Cecum and Appendix. The cecum and the appendix are located in the lower-right quadrant of the abdomen.

Colon. The colon absorbs excess water and salts into the blood. The remaining waste matter is converted to feces through bacterial action. The colon is divided into four major sections.

Click the icon to see an image of large intestine anatomy.

The first section, the ascending colon, extends upward from the cecum on the right side of the abdomen.
The second section, the transverse colon, crosses the upper abdomen to the left side.
The third section extends downward on the left side of the abdomen toward the pelvis and is called the descending colon.
The final section is the sigmoid colon.

Rectum and Anus. Feces are stored in the descending and sigmoid colon until they are passed through the rectum and anus. The rectum extends through the pelvis from the end of the sigmoid colon to the anus.

Causes

In most cases of colon or rectal cancers, the cause or causes are unknown. Defects in genes that normally protect against cancer play the major role in causing polyp cells to continuously spread and become cancerous. Some of these cases are caused by inherited genetic defects, and such patients usually have family histories of colorectal cancer. Most of the genetic mutations involved in colon cancers, however, appear to arise spontaneously (no strong family history) rather than being inherited. In such cases, environmental or other factors trigger genetic changes in the intestine that lead to cancer.

Inherited Genetic Factors

About 6% of cases of colon cancer are due to inherited factors.

APC Gene and Familial Adenomatous Polyposis (FAP). When the adenomatous polyposis coli (APC) gene is normal, it helps suppress tumor growth. In its defective form, it permits high levels of the protein beta-catenin to accumulate, which accelerates cell growth leading to polyps. Various genetic mutations that affect the APC gene directly or indirectly have been identified:

Familial adenomatous polyposis (FAP) is a rare and serious disorder in which the patient inherits an adenomatous polyposis coli (APC) mutation from either parent. It occurs in about 1 in 8,000 people. During early adulthood, hundreds to thousands of polyps grow in the colon. FAP causes less than 1% of all cases of colorectal cancer, but if untreated, virtually everyone who inherits this condition develops cancer before the age of 40. Many of the deaths attributed to FAP can be prevented with early and aggressive surgical treatment.
Non-inherited mutations of the APC gene have been detected in nearly all patients with spontaneous colon cancers.

Hereditary Nonpolyposis Colorectal Cancer (HNPCC). Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, accounts for at least half of colorectal cancers that run in families. (However, only 3% or less of all colorectal cancers are due to this problem). About 50 - 80% of people who inherit the abnormal gene will develop colon cancer. HNPCC tends to develop in the right side of the colon, often in young individuals. (Left-sided cancers can still occur as well.)

People who inherit HNPCC and other defects are prone to other cancers, including uterine and ovarian cancers, as well as cancers of the small intestine and kidney system (very rare). HNPCC is highly associated with genes containing an abnormality called microsatellite instability (MSI), which is a sign of defective DNA repair. Testing tumors for MSI in people with newly diagnosed colon cancer who also have a family history of the disease may prove to be an effective method for identifying patients with hereditary nonpolyposis colorectal cancer. Tests are being developed that can detect the actual HNPCC genetic abnormality (mutation) that was inherited from a father or mother. The two most commonly affected genes are MSH2 and MLH1.

Biochemical Factors Involved in Colon and Rectal Cancers

Cyclooxygenases and Prostaglandins. Cyclooxygenase 1 and 2 (COX-1 and COX-2) are enzymes involved in the production of prostaglandins, substances produced by the body that cause inflammation, widen and narrow blood vessels, control muscle contractions, and inhibit hormones that regulate fat metabolism. COX-2, but not COX-1, appears to play a role in the development and spread of colorectal tumors. COX-2 increases the levels of prostaglandin E2 (PGE2), which, in turn, stimulates factors that inhibit apoptosis, the natural process whereby all cells, including cancerous ones, self-destruct. It also activates interleukin-6 (IL-6), a factor in the immune system that is associated with cancer cell invasion.

C-Reactive Protein (CRP). CRP is another indicator of inflammation. In a 2004 study published in the Journal of the American Medical Association, elevated CRP levels predicted the development of colon -- but not rectal -- cancer.

Bile Acid Salts. Deoxycholic acid, which is found in the fat-digesting bile salts released by the gallbladder, appears to have carcinogenic properties. Its effects are now believed to play a role in some cases of colon cancer. Levels of the acid can rise as a result of high-fat diets or certain diseases.

Growth Factors. Chronically higher circulating levels of growth factors, including insulin-like growth factor, have been associated with colorectal cancer.

Inflammatory Bowel Disease

Inflammatory bowel diseases include Crohn's disease and ulcerative colitis. These chronic disorders cause persistent injuries in the intestinal tract that can, in some cases, produce cancerous changes.

Symptoms

It is possible to have colon or rectal cancer without symptoms. Many patients are free of symptoms until their tumors are quite advanced.

Weight Loss and Changes in Bowel Movements

Weight loss and changes in bowel movements are general symptoms for colon cancer, but these symptoms also occur in many other diseases.

Rectal Bleeding

Blood in the stools is a common sign of many intestinal cancers. It may appear red if it is fresh or black if it is old. It should be reported to a doctor immediately, even though it is often caused by conditions other than cancer, including:

Hemorrhoids
Minor tears around the rectal or anal areas
Diverticulosis

In addition, stool can change color by:

Eating certain red foods, such as beets or red licorice (red)
Taking iron supplements and medications that have bismuth subsalicylate, most commonly Pepto-Bismol (black)

Nevertheless, blood in the stools is an abnormal finding that should never be ignored. Always report it to your doctor for further advice.

Symptoms of Cancers in Specific Areas of the Colon

Symptoms of colorectal cancer vary widely depending on the location of the cancer within the large intestine.

Tumors in the Cecum and Ascending Colon (Right Colon). The waste matter in the first portion of the colon is in liquid or semi-liquid form. Tumors that develop here do not change bowel habits or stool formation, but they may cause intermittent or chronic bleeding. Although the stools look normal, patients may develop symptoms of anemia from iron deficiency. Such symptoms include weakness, fatigue, heart palpitations, shortness of breath, and exercise intolerance.

Tumors in the Transverse Colon. As waste material passes across the upper quadrants of the abdomen (the transverse colon), the intestine absorbs water, and the waste matter becomes more solid. In addition to bleeding, tumors here may cause cramps, gas, partial or complete obstruction, and even perforation of the bowel. Anemia can also occur.

Tumors in the Descending Colon and Rectum (Left Colon). When tumors partially block the lower intestine, thin, pencil-shaped stools may form. Bowel habits can change. Tumors in the rectum and lowest part of the intestine can cause pain and a feeling of fullness. Defecation may be painful, or patients may feel the urge to defecate but nothing happens. Bleeding from these locations may be brisk and bright red or maroon, but cancer is often detected before symptoms of chronic anemia develop.

Risk Factors

Colorectal cancer is the third most common cancer in the U.S., with Americans facing a lifetime chance of 5.5 - 6% for this cancer. In 2007, colorectal cancer was expected to cause 153,760 new cases and 52,180 deaths in the United States. About 73% of cancers occur in the colon and 27% in the rectum.

Sex

The lifetime risk of cancer of the colon or rectum is 5.9% for men and 5.5% for women.

Age

Colorectal cancer risk increases with age. More than 90% of these cancers occur in people over age 50. The rate of colorectal cancer in patients under 20 years is less than 1 in 100,000 per year. At age 50 about 1 in 2,000 people per year will develop colorectal cancer. After age 65, this rate increases to almost 3 in 1,000.

Ethnicity

African-Americans have the highest risk of being diagnosed with, and dying from, colorectal cancer. Among Caucasians, Jews of Eastern European (Ashkenazi) descent have an elevated rate of colorectal cancer. Asian Americans/Pacific Islanders, Hispanics/Latinos, and American Indians/Alaska Natives have a lower risk than Caucasians.

Family History

About 20 - 25% of colorectal cancers occur among people with a family history of the disease. (Seventy-five percent of cases are due to other causes.) People who have more than one first-degree relative (sibling or parent) with the disease are especially at high risk. The risk is even higher if the relative was diagnosed with colorectal cancer before the age of 60.

About 5 - 10% of patients with colorectal cancer have an inherited genetic abnormality that causes the disease. Genetic mutations associated with colorectal cancer include familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer.

Lifestyle Factors

The risks for colon cancer are far higher in industrialized nations than less developed countries. A Western lifestyle, being sedentary, smoking, and having excess weight have all been associated with increased risk for colorectal cancer. (However, about 75% of cases occur without a known predisposing factor.)

Dietary Factors. Eating a lot of red meat increases the risk for colorectal cancer. Other types of animal protein (low-fat dairy products, fish, poultry) may decrease the risk of developing polyps and colorectal cancer. Studies on fruits, vegetables, and fiber are mixed. Some evidence suggests that diets very low in fruits and vegetables may increase the risk. In any case, eating a variety of fruits and vegetables should be part of a healthy diet.

A 2007 study in the Journal of the American Medical Association suggested that diet may play a role in colorectal cancer recurrence, as well as prevention. The study evaluated patients with stage III colon cancer who had been treated with surgery and chemotherapy. Patients who ate diets high in red and processed meats, refined grains, and sweets had a higher risk of cancer recurrence and poorer survival than patients whose diets were high in fruits and vegetables, poultry, and fish.

Alcohol and Smoking. Alcohol use and smoking increase the risk for colorectal cancer. Patients who smoke and drink may also be diagnosed with colorectal cancer at a younger age than non-drinkers and non-smokers. Several studies suggest that women who smoke are at especially high risk of developing colorectal cancer.

Obesity. There is a demonstrated link between body mass and colon cancer risk for both men and women. The Centers for Disease Control and Prevention has reported that the risk of colon cancer rises as body mass index increases. Obesity has been associated biologically with higher circulating levels of insulin and a hormone called insulin-like growth factor. Chronically high levels of these substances may increase colorectal cancer risk.

Physical Inactivity. More than 50 studies from around the world suggest that physical activity helps prevent colon cancer. In contrast, exercise does not protect against rectal cancer.

Risk Factors for People with Inflammatory Bowel Disease

Crohn's disease and ulcerative colitis are chronic afflictions of the large intestine known as inflammatory bowel diseases (IBD). Both have been linked to increased risk for colorectal cancer. (Patients with ulcerative colitis have a higher risk than those with Crohn's disease.) Family histories are helpful in determining risk associated with inflammatory bowel disease. Some studies suggest the following:

Patients with IBD who have a family history of colorectal cancer face up to a five-fold risk of colon cancer themselves.
Individuals without IBD who have relatives who suffered from both IBD and colorectal cancer may face a higher risk for developing colorectal cancer themselves.
Individuals without IBD but with a family history of IBD and no colon cancer most likely face no higher risk for cancer themselves.

Crohn's disease, also called regional enteritis, is a chronic inflammation of the intestines that is usually confined to the terminal portion of the small intestine, the ileum. Ulcerative colitis is a similar inflammation of the colon, or large intestine. These and other inflammatory bowel diseases have been linked with an increased risk of colorectal cancer.

Other Risk Factors

Polyps. Polyps are tissue growths, usually benign, that develop in the color or rectum, most often in patients over 50 years of age. When pathologists examine polyps removed from the colon, they classify them as either hyperplastic or adenomatous. Both types are benign, but some adenomas will become malignant. As a preventive measure, polyps should be removed (polypectomy).

Ureterosigmoidostomy. People who have had ureterosigmoidostomy, a surgical procedure to correct a birth defect in the bladder or to treat some bladder cancers, may develop tumors near the site of the defect, which is chronically exposed to urine and feces. Such patients have a 5 - 10% chance of developing colon cancer 15 - 30 years after the operation.

Diabetes. Many studies have identified an association between type 2 diabetes and colon cancer. Both diseases share common risk factors of obesity and physical inactivity, but diabetes itself is a risk factor for colorectal cancer. Both men and women who have diabetes are at risk.

Heart Disease. Coronary artery disease (CAD) increases the risk for colorectal cancer. Both CAD and colorectal cancer share important risk factors, including smoking, high fat diet, sedentary lifestyle, and obesity.

Dietary Factors

Fruits, Vegetables, and Whole Grains

Some, but not all, studies have suggested that a high intake of fruits and vegetables can lower the risk for colorectal cancer. One study, for example, reported that these foods do not prevent polyps from forming but may help prevent them from becoming cancerous.

Phytochemicals. Many studies have demonstrated the cancer-fighting effects of plant chemicals called phytochemicals. Fruits and vegetables that contain phytochemicals can often be identified by colors:

Dark green (broccoli, spinach, kale, collard greens, mustard greens). These vegetables contain chemicals called isothiocyanates, which have been associated with a lower risk for cancer in general.
Red (red pepper, tomatoes, watermelon, raspberries, pink grapefruit). Lycopene is a chemical found in these foods that may have strong cancer-protective properties. Cooking tomatoes appears to increase their benefits.
Yellow-orange (carrots, pumpkin, sweet potatoes, oranges, tangerines). The colors in these foods are due to carotenoids. Carotenoids have been associated with health protection, although they may not have much effect on colon cancer itself.
Blue-black (many berries). Dark berries appear to have potent antioxidant chemicals that may be protective against cancer.

Organosulfurs are important food chemicals that are part of the allium family. Studies have reported health benefits from foods containing them. These compounds are found in garlic, leeks, onions, chives, scallions, and shallots. A review of 300 studies concluded that people who eat raw or cooked garlic regularly experience about two-thirds the risk of colorectal cancer as people who eat little or none. Another analysis, however, found the available evidence about garlic to be inconclusive. Garlic supplements, in any case, do not appear to be protective.

Fiber. Studies have been mixed on whether fiber (found in fruits, vegetables, and whole grains) protects the colon from cancer. For example, three major studies in 2002 and 2003 reported no difference in the development of colorectal polyps or cancer recurrence with high intake of fiber. On the other hand, results of the 2003 European Prospective Investigation into Cancer and Nutrition (EPIC) -- the largest study ever conducted on the role of diet in the development of cancer -- suggested that fiber is protective regardless of its source. However, in the study, the greatest benefits were observed for the left side of the colon and the least for the rectum. In any case, fiber, which is only found in plant products, may be beneficial for the heart and have other health advantages.

Fats and Oils

The role of fats in inflammatory bowel disease is complex and not fully known. A 2006 study from the Womens Health Initiative found that a low-fat diet did not help reduce the risk for colorectal cancer. However, the study did not distinguish between types of fat.

Monounsaturated fats (olive, peanut, canola oils; avocados, nuts) and omega-3 polyunsaturated fats (fish, flaxseed oil, walnuts) are the healthiest types of fats.
Saturated fats (red meat, butter, high-fat dairy products) and trans-fats (hydrogenated fat found in snack foods, fried foods, commercial baked goods) are unhealthy types of fats.

Dietary guidelines recommend that adults limit the total fat in their diet to 25 - 35% of total daily calories. Saturated fat intake should be less than 7%, and trans fats less than 1%, of total daily calories. (Patients with heart disease or diabetes may need to limit unhealthy fat in their diet even further.) Most fats should come from polyunsaturated and monounsaturated fat sources.

[See In-Depth Report #43: Heart healthy diet; and #42: Diabetes diet.]

Meat and High-Temperature Cooking

Evidence strongly suggests that red meat raises the risk for colon cancer development, and perhaps also recurrence. Red meat contains dietary iron, which has been associated with a higher risk for colon cancer.

High-temperature cooking (grilling, broiling, or pan-frying) has been specifically associated with increased risk for colon polyps and colon cancer. Overcooking meat increases the amount of carcinogens called heterocyclic amines, which has been associated with cancerous changes.

Dairy Products and Calcium

Milk, Lactose, and Probiotics. In one study, adults who drank the most milk had the lowest risk for colon cancer. A 2004 study published in the Journal of the National Cancer Institute supported this conclusion. In this review of 10 epidemiologic studies that included more than 500,000 people, those who consumed more milk and calcium had a lower risk of developing colorectal cancer. Milk contains not only calcium but also other compounds, such as lactose, that may help protect against colon cancer.

Yogurt specifically has been associated with a lower risk for colon cancer if it contains live active bacterial cultures, such as Lactobacillus acidophilus, that are called probiotics. These "friendly bacteria" appear to protect the colon from cancerous changes. (Acidophilus and other probiotic capsules are also available in health food stores.)

Calcium. Calcium, which is found in dairy products, is associated with colon cancer protection. Many studies have shown a possible protective effect from either high-calcium diets or calcium supplements. However, a 2006 study from the Womens Health Initiative found that calcium and vitamin D supplements do not reduce womens colorectal cancer risk. Many doctors still recommend that postmenopausal women take these supplements for bone health.

Total Calories and Sugar

Obesity has been associated with colon cancer. In some studies of people under 67 years old, the amounts of fat and protein were less important than the total number of calories consumed: the higher the energy intake, the greater the risk for developing colon cancer. In older adults, high calorie intake did not make any significant difference. Other studies have indicated that eating too much sugar may increase the risk for colon cancer.

Coffee and Tea

Studies conducted in several countries have found that drinking four or more cups of coffee a day is associated with a lower risk for colorectal cancer. Green tea may have also beneficial properties, but more research is needed in both of these areas.

Vitamin and Mineral Supplements

Folate and B Vitamins. For years, many doctors have believed that the B vitamin folate (called folic acid) may help protect against colorectal cancer, particularly for people who are genetically predisposed to this disease. Folate is found in beans, citrus fruits, and green vegetables, but some studies have indicated that the greatest protective benefits come from taking supplements.

However, an important study published in 2007 in the Journal of the American Medical Association challenged this assumption. The study suggested that high-dose folic acid supplements do not prevent colorectal cancer, and may actually increase the risk for developing certain types of colorectal tumors. The study evaluated over 1,000 men and women who had a recent history of non-cancerous colorectal polyps. (Adenomatous polyps, also called colorectal ademomas, are the most common type of polyp found in colorectal cancer screenings.) The results indicated that patients who took 1 mg/day of folic acid supplements were more likely to develop new adenomatous polyps than patients who did not take supplements. Patients in the folic acid supplement group were also more likely to have advanced adenomas and more numerous adenomas.

Adenomatous polyps are benign tumors, but they can potentially develop into cancerous tumors. Researchers are continuing to investigate the role that folic acid plays in colorectal cancer risk and prevention. It is possible that folic acid may help prevent the initial appearance of adenomatous polyps, but increase the risk for additional polyp formation once they have begun to occur.

Antioxidant Supplements. Antioxidants are chemicals that help eliminate harmful particles called oxygen-free radicals that have been associated with cancerous changes. Some studies have associated supplements of the antioxidants selenium and vitamins A, C, D, and E with lower colon cancer risk, but most studies have found no protective effect.

Prevention

Exercise

Studies indicate that daily exercise is one of the best ways to reduce the risk of colorectal cancer. The more vigorous the activity, the greater the benefit, but even moderate exercise (walking, stair-climbing) can help reduce colorectal cancer risk. The American Cancer Society (ACS) recommends that people engage in at least moderate exercise for 30 minutes or more at least 5 days a week. The ACS also notes that 45 minutes or more of moderate-to-vigorous activity at least 5 days a week may help further reduce cancer risk.

Some studies also suggest that regular exercise may be beneficial for patients who have been diagnosed with colorectal cancer. Two 2006 studies indicated that exercise may reduce the risk of colorectal cancer recurrence and death for patients with stage I - III cancer.

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

Nonsteroidal anti-inflammatory drugs (NSAIDs) are very common pain relievers that are available over-the-counter and by prescription. They include aspirin, ibuprofen (Motrin), naproxen (Aleve), and the COX-2 inhibitor celecoxib (Celebrex). Several studies have reported that NSAIDs help reduce the risk of colorectal cancer. However, regular use of NSAIDs, even in low doses, can increase the risk of gastrointestinal bleeding and stomach ulcers. Long-term use of NSAIDs can also increase the risk for heart attack and stroke, especially in people who have a history of heart disease. Several 2006 and 2007 studies in the New England Journal of Medicine reported that celecoxib prevented precancerous polyps, but the drug more than doubled patients risk for heart attack and other cardiovascular events.

A 2005 Nurses Health Study found that aspirin, but not other NSAIDs, does provide protection against colorectal cancer. However, the risk was only reduced for women who took 2 aspirin a day for more than 10 years. In addition, this dose level greatly increases the risk for gastrointestinal bleeding. Furthermore, a 2007 study in the New England Journal of Medicine suggested that aspirins protective effects may only apply to some types of colorectal cancer tumors. Another 2007 study, published in the Lancet, indicated that long-term daily use of aspirin can protect against polyps and colorectal cancer, but experts agree that aspirins risks do not outweigh its benefits for most people. (Some people who are at high risk for developing colorectal cancer may benefit from aspirin therapy.)

In March 2007, the U.S. Preventive Services Task Force (USPSTF) recommended against the routine use of aspirin and other NSAIDs to prevent colorectal cancer in people at average risk for this disease. (This recommendation does not apply to people who have a family history of colorectal cancer or who are at high risk for developing colorectal cancer due to other risk factors.) Long-term use of NSAIDs can increase the risk for gastrointestinal bleeding, kidney function problems, and heart problems. Aspirin can also increase the risk for hemorrhagic stroke. Due to these risks, the American Cancer Society and other professional associations also recommend against the use of NSAIDs or other types of medications for colorectal cancer prevention.

5-ASAs

Medications containing 5-aminosalicylate (5-ASA) are sometimes given to patients with ulcerative colitis to help control inflammation. These drugs, which include sulfasalazine and mesalamine, are chemically related to aspirin. A 2005 review of clinical trials found that patients with ulcerative colitis who used 5-ASA were 49% less likely to develop colorectal cancer than patients who did not use these drugs

Statins

Some studies have suggested that cholesterol-lowering statin drugs may help reduce colorectal cancer risk. A 2006 study in the Journal of the National Cancer Institute did not find any protective benefit for statins.

Estrogen in Women

Estrogen has been associated with a lower risk for colon cancer, perhaps because of specific enzymes that prevent cell proliferation. Drugs containing estrogen, then, may help high-risk women:

There is some evidence that hormone replacement therapy (HRT) reduces the risk of colon cancer in postmenopausal women. It carries other risks, however, including a higher risk for breast and uterine cancer and blood clots. A 2004 New England Journal of Medicine study found that while short-term use of estrogen plus progestin reduced the risk of developing colon cancer, combination HRT users who were diagnosed with the disease had more advanced forms of the cancer. Older women who are at higher risk for colon cancer might discuss risks and benefits of HRT with their doctor.
Oral contraceptives may reduce younger women's risk of colon cancer. Duration of use does not seem to be associated with decreased risk, but protection appears stronger for women who have more recently used oral contraceptives.

Diagnosis

Colon and rectal cancers are diagnosed using the screening tests discussed below. These tests can detect precancerous polyps and colorectal cancers at stages early enough for complete removal and cure.

Unfortunately, only 30 - 40% of adults over 50 years old (mostly in the upper socioeconomic group) have regular screening tests that could detect a cancer early enough for curative treatment. A survey reported that many people are not screened because they are too embarrassed. Those who had already had the tests were willing to have them again if they saved one additional day of their lives.

There is some debate about what is the best screening method. Current screening guidelines offer several different options for patients. Doctors agree that not enough people are screened and that these tests, if adopted with the same regularity as such screening tests as Pap smears, would save many lives. It is especially important for anyone at increased risk or with symptoms, such as rectal bleeding or ulcerative colitis, to have testing at an earlier age.

There is also debate about when people should stop being screened. A 2006 study in the Journal of the American Medical Association indicated that screening provides little benefit for elderly people, especially because colorectal cancers grow very slowly. The researchers suggest that doctors should carefully consider the risks versus benefits of screening patients age 80 and older.

General Screening Guidelines

Individuals should discuss with their doctors the risks and benefits of all screening procedures. Some controversy exists over how often people without risk factors for cancer should be screened and which detection method should be used for them.

Guidelines for Adults Age 50 and Over with Average Risk. The following are the five screening options recommended for people age 50 and over who have no symptoms and no family history of colon cancer:

Fecal occult blood test (FOBT) or fecal immunochemical test (FIT) every year
Flexible sigmoidoscopy every 5 years
FOBT or FIT every year plus sigmoidoscopy every 5 years
Double-contrast barium enema every 5 years
Colonoscopy every 10 years

Choosing between Colonoscopy and Sigmoidoscopy. The choice between colonoscopy and sigmoidoscopy for routine screening for older adults with average risk is an area of intense debate. The issues are as follows:

Sigmoidoscopy is less costly, less invasive, quicker, and safer than colonoscopy. Although it allows inspection of only the left side of the colon, any abnormal findings from sigmoidoscopy trigger a full colonoscopy. Therefore, experts estimate that sigmoidoscopy can detect 80% of all significant problems.
Colonoscopy is more sensitive than any other current screening method for detecting colon cancer. It can find 75 - 90% of colorectal cancers. If the goal were to reduce the number of cancer cases, regardless of cost, colonoscopy would be the preferred approach. Colonoscopy, however, is more expensive than sigmoidoscopy and has a slightly higher risk for complications (bowel tears or bleeding when a polyp is removed).

There are 3 basic tests for colon cancer: a stool test (to check for blood), sigmoidoscopy (inspection of the lower colon), and colonoscopy (inspection of the entire colon). All 3 are effective in catching cancers in the early stages, when treatment is most beneficial.

Screening, particularly with colonoscopy, in increased- and high-risk populations can save lives. The most important risk factors are a family history of colorectal cancer and personal history of colorectal cancer, polyps, or chronic inflammatory bowel disease. People with these risk factors should be screened before age 50 and may need more frequent screenings.

Guidelines for Increased-Risk Groups. Anyone with first-degree relatives diagnosed with colon cancer younger than 60, or with two relatives who have been diagnosed with colon cancer at any age, should consider beginning the standard screening regimen with a colonoscopy every 5 years, beginning at age 40 or 10 years before the youngest case in the family (whichever is earlier).

Men of African descent are also considered to be at increased risk for colon cancer and should discuss similar screening guidelines with their doctors.

Guidelines for High-Risk Groups. The following guidelines may be useful for specific high-risk groups.

People who have the mutated hereditary nonpolyposis colorectal cancer gene (MSH2 or MLH-). Frequent colonoscopy (for instance, every 1 - 2 years) beginning in their early 20s. (Regular screening for other cancers, such as uterine cancer, is also reasonable.)
People who have the mutated familial adenomatous polyposis (FAP) gene. Frequent screening with endoscopy (flexible sigmoidoscopy or colonoscopy) beginning in early puberty. Genetic testing is now recommended for family members of people with known FAP.
People with predisposing intestinal problems, such as widespread and active ulcerative colitis or Crohn's disease. Annual screening with colonoscopy with biopsies of suspicious areas.

Guidelines for Follow-Up After Detection of Precancerous Polyps. Patients who have had a previous examination in which polyps were detected (and removed) should have a repeat colonoscopy 1 - 3 years later, depending on the size, number, and type of polyps removed.

Digital Rectal Examination

The digital rectal examination is used to detect tumors in the rectum, lower intestine, and prostate gland. The doctor inserts a lubricated-gloved finger into the patient's rectum and feels for lumps or other abnormalities. The exam is quick and painless but embarrassing for some. Fewer than 10% of colon cancers develop within the region that can be evaluated by a DRE, so it is not useful as a sole screening test.

Fecal Occult Blood Test

Blood in bowel movements is not always visible, in which case it is called occult (hidden) blood. Fecal occult blood tests (FOBTs) are used to detect this hidden blood. The most common FOBT method is called the guaiac-based test. The patient is asked to supply up to six stool specimens in a specially prepared package. A small quantity of feces is smeared on specially treated paper, which reacts to hydrogen peroxide. If blood is present, the paper turns blue.

Accuracy. FOBTs can miss more than 75% of advanced cancers. Nevertheless, large studies have indicated that this simple test, performed annually, saves lives and may reduce the risk of dying from colon cancer by 15 - 33%. The following factors may affect its accuracy:

The levels of iron in the blood can affect results. Patients should not take iron supplements or eat red meats several days before the test.
Certain raw fruits and vegetables that contain the chemical peroxidase (cauliflower, horseradish, radishes, melons, and turnips) can cause a positive test reaction even if no blood is present.
Aspirin and NSAIDs are anticoagulants that can cause minor bleeding. They should not be taken for a week before the test. However, a 2005 study suggested that the prescription anticoagulant warfarin does not affect FOBT results.
Vitamin C and foods rich in this vitamin may cause a false negative reaction and should be avoided a few days before the test.
Bleeding from other causes, such as menstruation, hemorrhoids, gingivitis, or urinary infections, can produce blood in the stools and affect results.

Even if none of these conditions is present, a test that shows hidden blood does not necessarily mean that cancer is present. About 20 - 30% of people with occult blood have noncancerous polyps or other conditions, such as gastritis, and only 5 - 10% actually have cancer. Any abnormal result, however, requires further testing, such as colonoscopy.

Lack of Compliance. Compliance is a major problem. Patients are asked to perform the tests at home and send the test cards to the laboratory. Only 35 - 50% of patients actually follow through. Occult-blood tests that give results at home are available but are extremely inaccurate. In one large study, these tests failed to detect advanced cancer in about 62% of cases, although they may detect some early cancers.

Visualizing the Colon: Colonoscopy, Sigmoidoscopy, and Barium Enema

If a digital rectal exam (DRE) or fecal occult blood test (FOBT) shows signs of trouble, several methods to visualize the colon are available. They include colonoscopy, sigmoidoscopy, and double-contrast barium enema. They have the following similarities and differences:

Sigmoidoscopy can only view the rectum and the left side of the colon, while colonoscopy and barium enemas allow a view of the entire large intestine.
Both flexible sigmoidoscopy and colonoscopy involve snaking a fiber optic tube through regions of the rectum and colon to view the walls of the intestine. The tube contains a tiny camera that transmits the image to a video screen. The use of an ultrasound (sound wave) scanner is proving to enhance viewing quality. Barium enemas simply use x-rays.
During either sigmoidoscopy or colonoscopy, the doctor is able to remove polyps or other abnormalities revealed by these procedures with surgical instruments inserted through the tube. It is not possible to remove polyps with a barium enema, which is not invasive.

Sigmoidoscopy. Sigmoidoscopy examines the rectum and the lower two feet of the colon. It cannot, however, detect the roughly half of cancers that occur in the right colon. Right-sided cancers are more common in older people.

The procedure uses a flexible fiber optic tube (it is thus referred to as flexible sigmoidoscopy) that contains a tiny camera and surgical instruments.
It lasts about 10 minutes and may be mildly uncomfortable, but it is not painful and is generally very safe. In one study, 70% of patients reported that the procedure was far less unpleasant than they had expected.

This procedure has been found to reduce the risk of fatal cancers in the rectal and sigmoid area by 60%. If polyps are detected, a colonoscopy is then used.

Colonoscopy. Colonoscopy is the most accurate testing method and can reduce cancer incidence by up to 90%. It is clearly indicated for anyone with an increased risk for colorectal cancer, including those with a personal or family history of the disease. As with sigmoidoscopy, a colonoscopy uses a flexible tube, but it is snaked through the entire large intestine.

For about a day before the procedure the patient eats nothing and drinks a laxative solution that cleans out the colon. The taste of the solution is unpleasant, although it has improved in recent years.
The procedure typically uses a sedative that produces a "twilight" sleep and often makes the procedure more comfortable than sigmoidoscopy.
Air may be introduced into the intestine to widen it and allow the tube to navigate curves. A colonoscopy avoids the risk of radiation associated with a barium enema, but it is important to note that even a colonoscopy does not detect all cancers.

Complications are rare, but include the following:

Hyponatremia. Hyponatremia is a low concentration of sodium in the blood. The complication may be caused by the effects of bowel cleaning before the procedure that can result in water retention and reductions in sodium. When severe, it can cause temporary neurological symptoms, such as confusion, lethargy, unsteadiness, and slurred speech. Researchers suggest that sodium concentrations be measured in patients who develop such symptoms after colonoscopy.
Bowel perforation (very low risk, about 2 in 1,000 procedures). The risk for bowel perforation is greater with colonoscopy than flexible sigmoidoscopy.
Bleeding at the site of biopsy or polyp removal.

Overall, colonoscopy is a safe procedure. However, according to a 2006 study in the Annals of Internal Medicine, serious complications occur in about 5 of every 1,000 colonoscopies. Most of these complications occurred when a biopsy or polyp removal was performed. (The risk for complications without biopsy or polyp removal is about 1 in every 1,000 colonoscopies.) This study looked at colonoscopies in general, including those that are done to diagnose the causes of a patient's symptoms. The risk may be lower for colonoscopies performed solely to screen for colorectal cancer.

Barium Enema. The double-contrast barium enema, which uses an x-ray image, is the less expensive alternative for viewing the entire colon. It is not as accurate as colonoscopy, and if any polyps or abnormalities are revealed on x-ray, a colonoscopy is then required to remove suspicious tissue, so it is now recommended much less often than in the past.

The barium enema is a valuable diagnostic tool that helps detect abnormalities in the large intestine (colon). The barium enema, along with colonoscopy, remains the standard in the diagnosis of colon cancer, ulcerative colitis, and other diseases of the colon.

Genetic Screening

Screening for familial adenomatous polyposis. Genetic screening for familial adenomatous polyposis (FAP) and hereditary nonpolyposis colon cancer (HNPCC) is now available and may be recommended for high-risk patients. The test for FAP detects a mutation in the adenomatous polyposis coli in up to 90% of people who carry it. Testing for HNPCC mutation is somewhat more complex.

Screening for insulin-like growth factor. A gene that regulates insulin-like growth factor (IGF-2) is functional during fetal development and then becomes inactive. Some evidence now suggests that people who have IGF-2 in adulthood have a higher risk for colon cancer. Blood tests for detecting IGF-2, then, may be helpful in identifying patients who should have more intensive screening. Currently, however, this is only used as a research tool.

Stool DNA Testing. A promising technique for colorectal cancer screening is the detection of altered DNA in cancer cells that have shed from the colon and are excreted in the stool. Such tests may prove to detect both inherited and noninherited genetic mutations. This may become a widely used tool in the future. However, larger clinical studies are needed.

Experimental Screening and Diagnostic Methods

Virtual Colonoscopy. A promising experimental technique called virtual colonoscopy allows three-dimensional imaging of the colon without using invasive instruments. As with standard colonoscopy, the patient takes a laxative first to clear out the intestine. The procedure itself involves pumping air into the colon and scanning the intestine using computed tomography (CT). It is very safe and takes about only 10 minutes. The procedure is similar in accuracy to conventional colonoscopy for detection of larger polyps (6 mm or more in diameter) and is also potentially less expensive. Colonoscopy is required, however, if suspicious areas are found, which may occur frequently with the CT procedure, since it erroneously identifies a high number of nonexistent polyps.

A study published in April 2004 in the Journal of the American Medical Association compared results of standard colonoscopy versus virtual colonoscopy in over 600 patients at nine major medical centers. Virtual colonoscopy had much lower rates of successfully finding polyps than standard colonoscopy. Virtual colonoscopy detected polyps of at least 6 mm in 39% of patients and polyps of at least 10 mm in 55% of patients. By contrast, standard colonoscopy detected 99% of polyps of at least 6 mm, and 100% of polyps of at least 10 mm. In addition, accuracy rates varied widely among the different hospitals. The authors advised that until more improvement in training and technique is achieved, virtual colonoscopy "is not yet ready for widespread clinical application."

Magnetic Resonance Colonography. Magnetic resonance colonography (MRC) is another non-invasive technique for visualizing the colon. The patient receives an enema containing a contrast substance, and then magnetic resonance images are taken. MRC is fast, comfortable, and less invasive than colonoscopy. Currently, however, there is a poor detection rate for flat tumors and for polyp tumors less than 10 mm in diameter.

Staging

A diagnosis of cancer will lead to staging and other tests to help determine the outlook and the appropriate treatments.

The large intestine is a long hollow organ lined with mucous membrane (mucosa). Muscle layers wrap around the entire length and help move food material through to the rectum.

Staging

Unlike many other cancers, the size of the tumor is not a major factor in determining the outcome of colorectal cancer. Of greater importance is how far the cancer has spread. To determine this, doctors will assign a stage to the tumor. There are several methods for staging. The older system, known as Dukes', categorizes four basic stages: A, B, C, and D. A more recent system refers to these stages as I, II, III, and IV but divides the categories slightly differently. The term "5-year survival" means that patients have lived at least 5 years since diagnosis. Most patients who live 5 years without a recurrence are considered to be cured of their disease.

Stages of Colorectal Cancer
Stage	Condition	5-Year Survival
A or I	Tumor superficially involves the inner lining of the intestine.	More than 90%
B or II	Tumor has penetrated through the muscle wall of the intestine but has not reached the lymph nodes.	70 - 85%
C or III	Lymph nodes are involved.	65% or below
D or IV	Tumor has spread to other organs (metastasized), usually the liver first.	5 - 9%

Click the icon to see an image of the stages of cancer.

Tumor Markers

Researchers are continually seeking to identify tumor markers, substances (usually found in blood samples) that will assist in the diagnosis of cancer and in monitoring effects of treatment.

Carcinoembryonic Antigen. High blood levels of a protein called carcinoembryonic antigen (CEA) sometimes indicate the presence of colon cancer. Unfortunately, it is also elevated in other cancers and in some noncancerous conditions. CEA is not effective as a screening tool for healthy people, but might eventually be helpful for patients with cancer.

An advanced diagnostic technique called polymerase chain reaction (PCR) can detect genetic evidence of CEA. One study indicated that when these microscopic footprints of colon cancer are detected in the lymph nodes of patients with Stage II cancer (whose lymph nodes otherwise appear to be not involved with cancer), the outlook is similar to that of patients with Stage III cancer. Patients without this so-called micrometastasis have a very favorable prognosis. Further research is needed, however, before PCR can be used in widespread practice.
In patients with a history of, or active, colon cancer, follow-up measuring of blood CEA levels may be helpful in detecting recurrence of the cancer and effectiveness of treatments.

Defective P53 Gene. The presence of a defective p53 gene is a marker for very poor prognosis in patients with advanced colon cancer. In its normal state, the gene is important for regulation of cell growth. Testing for this abnormality, however, is not widely done because it is not clear how to use this information.

Other Tumor Markers. Other tumor markers under investigation include a protein called GLUT1, cancer antigen 19-9 (CA 19-9), matrix metalloproteinase-9 (MMP-9) RNA, HER-2/neu oncoprotein, transforming growth factor beta-1 (TGF-beta-1), and CD44.

Click the icon to see an image of drawing blood for culture.

Sentinel Node Biopsy

A technique known as a sentinel node biopsy is increasingly performed by experienced surgeons in selected patients. This procedure is used to determine if cancer has spread beyond the nodes, possibly reducing the need for complete axillary lymphadenectomies. It involves the following:

The procedure uses an injection of a tiny amount of a tracer, either a radioactively-labeled substance (radioisotope) or a blue dye, into the tumor site.
The tracer or dye then flows via the lymphatic system into the so-called sentinel node. This is the first lymph node to which any cancer would spread.
The sentinel lymph node and possibly one or two others are then removed.
If they do not show any signs of cancer, it is highly likely that the remainder of the lymph nodes will be cancer free, and further surgery becomes unnecessary.

It is still not known if the sentinel node biopsy has any survival advantages compared to the standard procedures with lymph nodes removal. However, one study indicated that careful and complete removal of potentially cancerous lymph nodes is still very important for improving survival in patients with Stage II and III colorectal cancer.

PET/CT Scans

Whole-body imaging scans that combine positron emission tomography (PET) and computed tomography (CT) may be helpful in accurately staging colorectal cancer, according to preliminary research published in 2006 in the Journal of the American Medical Association.

Prognosis

Survival Rates

Survival rates for colorectal cancer have been rising in recent years. The 5-year survival rate is as high as 90% for cancer that has not spread to the lymph nodes (localized cancer). When cancer has spread to lymph nodes and other parts of the body, survival rates drop to 65% and below. Because many cancers are detected at later stages, the overall survival rate is currently about 60%. African-Americans and other minorities tend to have lower survival rates than Caucasians. Studies suggest, however, these higher mortality rates are largely due to less access to optimal health care, including appropriate surgical care and aggressive treatments.

Factors in Treatment Success

In most cases, age is not a factor in treatment success. Good survival rates are achieved in the elderly as well as in young people. Chances for survival are less in Stage II cancers if the intestine is obstructed or perforated. If cancer has spread to lymph nodes (Stage III), the outlook is better if three or fewer lymph nodes are involved. Treatment can prolong life even when cancer has spread.

Surgery

Surgical removal of the tumor ("resection") along with any affected surrounding tissue is the standard initial treatment for potentially curable colorectal cancers (cancers that have not spread beyond the colon or lymph nodes). Drug and radiation therapy are often used for advanced cancers and are continuously being tested with surgery in different combinations and sequences.

Although choosing a qualified surgeon is critical, choosing a hospital experienced in procedures is also important. The more often colon cancer surgery is performed at a given hospital, the lower the mortality rate at that hospital is likely to be.

Colectomy

Unless cancer is very advanced, most tumors are removed by an operation known as colectomy:

Colectomy involves removing the cancerous part of the colon and nearby lymph nodes.
The surgeon then reconnects the intestine.
If the surgeon cannot reconnect the intestine, usually because of infection or obstruction, the surgeon will perform a colostomy. The need for colostomies is higher after surgery for rectal cancer. In most cases of colon cancer, colostomies are not needed. [See "Colostomy" below.]

Click the icon to see an illustrated series detailing colon cancer treatment.

The Surgical Approach. The standard technique for a colectomy is open, invasive surgery. Laparoscopy, sometimes called keyhole surgery, is a less invasive method. Laparoscopy is still considered an investigational technique for treating colon cancer, but it is gaining more acceptance and showing good results in clinical trials.

Open Surgery:

Open surgery uses a wide incision to open the patient's abdomen. The surgeon then performs the procedures with standard surgical instruments. This is the usual method for performing colectomy.

Laparoscopy:

Laparoscopy uses a few small incisions through which the surgeon passes a fiber optic tube (laparoscope) containing a small camera or tiny instruments. It is generally used for early colon cancer (for tumors less than 2 centimeters or for well-defined tumors less than 3 centimeters).
A 2004 New England Journal of Medicine study found that patients who received laparoscopic colectomy had similar rates of surgical complications, cancer recurrence, and survival as those who received traditional open surgery. However, the patients who had laparoscopy recovered faster and did not need as many narcotic painkillers.
Several 2005 studies indicated that laparoscopy works as well as conventional surgery for treatment of colon cancer. However, laparoscopy does not appear to be as effective for rectal cancer.

Click the icon to see an image detailing pelvic laparoscopy.

Click the icon to see an illustrated series detailing a resection of the large intestine.

Other Investigational Measures. Researchers are testing expandable metal tube-like devices called stents to keep the intestine open. Stents may be used before a procedure to allow bowel cleansing or for long-term use to keep open colons that can't be operated on.

Colostomy

A colostomy is performed in order to bypass or remove the lower colon and rectum. The procedure generally involves creating a passage, called a stoma, through the abdominal wall that is connected to the colon. The feces pass through this passage and are eliminated. Patients must learn how to care for the stoma and keep the area sanitary.

A colostomy usually will have one opening (single-barreled), or there may be two loops opening through the skin (double-barreled).

Usually the colostomy is temporary and can be reversed by a second operation after about 3 - 6 months. It the rectum and sphincter muscles in the rectum need to be removed, the colostomy is permanent. Permanent colostomies are more common when the cancerous regions are within 2 - 3 centimeters of the anus. Fortunately, surgical advances and knowledge of the extent of safe margins are reducing the need for permanent colostomies.

Click the icon to see an illustrated series detailing a colostomy procedure.

Managing Permanent Colostomies. In cases where the colostomy is permanent, the patient must wear a colostomy pouch, which sticks to the skin using a special glue. Pouches are available as one- or two-piece systems. The one-piece system is simpler, but the two piece system allows replacement of the pouch without removing the tape.

For best results, the pouch should be emptied when about one-third full. It should be replaced 1 - 2 times a week, depending on signs of leakage (itching or burning of the skin near the stoma). The pouches are odor proof.

Surgical Treatments for Rectal Cancer

Surgical treatments for cancer in the rectum are complex since they involve muscles and tissue that are critical for urinary and sexual function.

Local Excision or Polypectomy for Early Stages. In order to preserve the function of the anal sphincter and prevent the need for colostomy, Stage I and Stage II tumors may be removed by local excision, sometimes followed by chemotherapy and radiation. In this procedure, the tumor is cut out without removal of a major section of rectum. In some cases cancer recurs, but a second operation may be possible. Another treatment for early-stage rectal cancer, called electrocoagulation, destroys tumors using a high frequency electric current. It is being tested in clinical trials.

Radical Resection. In about a third of cases of rectal cancer, the cancer occurs in the lower part of the rectum, where between 70 - 80% of cancers have spread beyond the rectal wall. These patients need a radical resection, in which surrounding structures, including the sphincter muscles that control bowel movements, must often be removed.

The use of chemotherapy and radiation prior to surgery may prevent the need for permanent colostomy in some patients. This is an active area of clinical research, and trials are under way to address this issue. Another technique, called coloanal anastomosis, reconstructs the area to avoid the need for colostomy, and may be appropriate in some patients.

Total Mesorectal Excision. Total mesorectal excision (TME) involves dissection and removal of the entire cancerous area of the rectum along with surrounding fatty regions where the lymph nodes are located (the mesorectum). When successful, TME preserves the sphincter muscle, reducing the need for a permanent colostomy. Increasing use of this procedure is resulting in lower recurrence rates, lower levels of impotence and incontinence, and better overall survival rates compared to other resection techniques. Some experts now recommend it as a first choice for certain patients with locally advanced rectal cancer.

Combining chemotherapy and radiation either before or after TME is yielding promising long-term results and a low risk for local recurrence. There are many questions, however, and it is not clear which approach is better for specific patients.

Managing Side Effects and Psychological Repercussions

Side effects of colon surgery include:

Sexual dysfunction. This is of particular concern. In general, colostomy does not usually affect sexual function. However, wide rectal surgery can cause short- or long-term sexual dysfunction. Sildenafil (Viagra) may help men who experience this after surgery.
Irregular bowel movements.
Gas and flatulence. Pouching filters are available to reduce gas. Certain foods produce more gas than others -- usually within 6 - 8 hours after ingestion for colostomy patients. They include beans, oat bran, most fruit, and certain vegetables (cabbage, cauliflower, Brussels sprouts, broccoli, and asparagus). To prevent swallowing air, patients should avoid sipping through straws, chewing gum, and chewing with their mouths open.
Diarrhea.
Bladder complications.
Sense of urinary urgency.
Fecal incontinence. Patients with rectal surgery have a higher risk for bowel dysfunction than those who had a colostomy.
Complications in or around the stoma. These can occur early after surgery to many years after the procedure. They include skin infection or breakdown, hernias, narrowing of the stoma, bleeding, and collapse.

There are no dietary restrictions, although many patients avoid foods that can produce gas. Everyone should drink plenty of fluids and get sufficient fiber.

The potential side effects of sexual and bowel dysfunction for colorectal surgical patients can be devastating, although many patients do very well and live normal productive lives. Positive emotions play a strong role in recovery. Patients who are depressed should discuss with a doctor all aspects of treatment that affect the quality of life, and consider seeking support groups.

Medications

Chemotherapy uses drugs that kill cancer cells throughout the body. There are two situations in which chemotherapy is used:

The adjuvant setting. Adjuvant refers to the use of chemotherapy after surgery in patients with Stage III tumors and selected patients with high-risk Stage II tumors (disease that is potentially curable). The goal of this therapy is to eliminate any cancer cells that surgery may have missed, thereby preventing recurrence and increasing the chance of cure. Patients of all ages, including the elderly, can benefit.
In metastatic disease. In patients with metastatic disease (where the cancer has spread to other parts of the body) the goal of chemotherapy is to shrink tumors, improve symptoms and quality of life, and lengthen life.

In the adjuvant setting, there are some differences in chemotherapy treatments between colon and rectal cancers:

Chemotherapy for Stage II is considered standard care for Stage II rectal cancer but is under debate for colon cancer.
Chemotherapy is standard for patients with Stage III colon cancer. Chemotherapy is also standard for patients with Stage III rectal cancer but is used in combination with radiation.

Chemotherapy for Stage II Colon Cancer. Adjuvant chemotherapy for Stage II colon cancer is controversial. Such patients tend to have a good outcome after surgery, and the positive effects of chemotherapy have been difficult to demonstrate. To date, the survival advantage of adjuvant chemotherapy in this group has been reported to be only in the range of 2%. However, better trials are still needed to confirm or refute the benefits in specific patient groups.

Although not yet known with certainty, some data suggest that certain patients with Stage II cancer may be at higher risk of recurrence and would theoretically benefit from adjuvant therapy. These include patients with cancers that have:

Obstructed the bowel
Perforated the wall of the colon
Adhered to structures outside the intestine

Advanced diagnostic techniques are under investigation for helping to select appropriate candidates for adjuvant therapy. None of these methods, however, are ready to be used routinely to help make treatment decisions. The decision whether to pursue chemotherapy for Stage II disease should be made after careful discussion between the patient and their oncologist, especially after features, such as bowel perforation or obstruction, are taken into account.

Chemotherapy for Stage III Colon Cancer. Since the early 1990s, adjuvant chemotherapy with 5-FU and leucovorin has been the standard of care for Stage III colon cancer. In recent years, the FOLFOX (5-FU, leucovorin, oxaliplatin) regimen has also been used for chemotherapy following surgery. Numerous trials have shown that adjuvant chemotherapy in this setting reduces the absolute risk of death from colon cancer by about one-third and improves survival by 10%. Clinical trials are also investigating combinations of other drugs.

Chemotherapy for Advanced Colorectal Cancer. Chemotherapy is either given directly into the arteries of the liver or intravenously (through a vein) with 5-FU and leucovorin. Oxaliplatin is sometimes added, but recent evidence suggests that the targeted therapy biologic drug bevacizumab may be a better addition. Other alternative chemotherapy choices are capecitabine, or irinotecan combined with cetuximab. Radiation therapy may be used in place of chemotherapy or in combination with it. Studies indicate that chemotherapy offers only a modest improvement in survival, but may help reduce symptoms.

Chemotherapy Drugs and Regimens

Seven drugs are currently approved for colorectal cancer chemotherapy:

5-fluorouracil (5-FU, Adrucil), which is often given in combination with leucovorin (Wellcovorin). Leucovorin is a vitamin that helps boost the effectiveness of 5-FU.
Capecitabine (Xeloda)
Oxaliplatin (Eloxatin)
Irinotecan (Camptosar)
Bevacizumab (Avastin)
Cetuximab (Erbitux)
Panitumumab (Vectibix)

Capecitabine is a pill form of 5-FU. The other drugs are administered intravenously. Many of these drugs are given in combination with each other. Common chemotherapy combination regimens include:

5-FU / LV (5-FU and leucovorin)
FOLFOX (5-FU with leucovorin and oxaliplatin)
FOLFORI (5-FU with leucovorin and irinotecan)
IFL (Irinotecan, 5-FU, leucovorin)
XELOX (Capecitabine and oxaliplatin)

Side effects occur with all chemotherapeutic drugs. They are more severe with higher doses and increase over the course of treatment. Because cancer cells grow and divide rapidly, anticancer drugs work by killing fast-growing cells. This means that healthy cells that multiply quickly can also be affected. The fast-growing normal cells most likely to be affected are blood cells forming in the bone marrow, and cells in the digestive tract, reproductive system, and hair follicles. Nausea and vomiting is a very common side effect, but drugs such as ondansetron (Zofran) can help provide relief. In general, side effects are nearly always temporary, and medications can help manage them. Most patients are able to continue with normal activities for all but perhaps 1 - 2 days a month.

Specific Chemotherapy Drugs

5-Fluorouracil (5-FU) with Leucovorin. Adjuvant therapy using 5-fluorouracil, either alone or with leucovorin (5-FU/LV), is the standard treatment for patients with high-risk colon cancer (Stage III or select patients with Stage II tumors). Leucovorin, also called folinic acid, is a form of the B vitamin folic acid, which helps increase 5-FUs effectiveness. Patients are given a series of cycles that usually continue for at least 6 months.

There are many different ways of giving 5-FU, including intravenously over several hours once a week, intravenously daily for 5 consecutive days every month, or as continuous infusion with a portable pump.

The side effects can be quite different, depending on the way 5-FU is given, and women may be more susceptible than men. In one analysis, 53% of women and 40% of men experienced severe side effects, while response rates and survival were similar for both sexes. Many patients, however, tolerate 5-FU with leucovorin well, with manageable side effects. The most common side effects include nausea and vomiting, diarrhea, loss of appetite, hair loss, swelling of hands and feet, rashes, and mouth sores.

Irinotecan. Irinotecan (Camptosar) blocks an enzyme essential for cell division. Irinotecan can be given alone or in combination with 5-FU and leucovorin. This combination therapy (irinotecan plus 5-FU/LV) is also referred to as the "Salz regimen," or IFL. When it was approved in the mid 1990s, irinotecan was the first new drug developed for colon cancer in over 30 years. Studies have shown that irinotecan combined with 5-fluorouracil and leucovorin (5-FU/LV) significantly delays the time at which tumors progress and improves survival in metastatic cancer compared to 5-FU/LV alone. While the survival advantage is small, the combination has become the standard of care for metastatic cancer. Of concern, however, are studies that have reported an increased risk of death from toxic effects with the use of the three-drug combination. These deaths appeared to be related to blood-clotting complications. Doctors should carefully monitor dosages. Diarrhea is a common side effect of irinotecan.

Capecitabine. Capecitabine (Xeloda), an oral form of 5-FU, was approved in 2001 as a treatment for metastatic colorectal cancer. It is the only pill approved for colorectal cancer. A major 2005 study, published in the New England Journal of Medicine, found that capecitabine works as well as the standard 5-FU/LV regimen and causes significantly fewer side effects. The study involved patients with Stage III colon cancer who had undergone surgical removal of the tumor. In 2005, capecitabine was approved for postsurgical treatment of patients with Dukes C colon cancer. Capecitabine is also showing promise in combination with radiation therapy for rectal cancers.

Oxaliplatin. Oxaliplatin (Eloxatin) is related to cisplatin, a widely used platinum-based chemotherapy drug. Oxaliplatin is used in combination with 5-FU and leucovorin. (This triple combination therapy is called the FOLFOX regimen.) Oxaliplatin was first approved in 2002 for use in combination with 5-FU and leucovorin as a second-line treatment for cancer that has progressed after initial therapy.

Since 2002, oxaliplatin has received additional approvals as a first-line treatment for advanced colorectal cancer, and as a post-surgical treatment for patients who have undergone tumor resection.

Oxaliplatin can cause pain and tingling sensations in the hands and feet (neuropathy) that is worsened by exposure to cold. Recent research suggests that adding xaliproden (Xaprila) to the FOLFOX regimen may help reduce the frequency of neuropathy without interfering with the benefits of chemotherapy. Xaliproden is a drug used to treat the neurological disease amyotrophic lateral sclerosis (also known as Lou Gehrig's disease).

Bevacizumab. Bevacizumab (Avastin) was approved in February 2004 as a first-line treatment for patients with metastatic colorectal cancer (advanced cancer that has spread in the body). It is used in combination with IFL (irinotecan, 5-FU, leucovorin). Bevacizumab is a genetically engineered monoclonal antibody that targets and inhibits vascular endothelial growth factor (VEGF), a protein that regulates angiogenesis (the development of new blood vessels that feed a tumor's blood supply). It is the first anti-angiogenic therapy approved for the treatment of colorectal cancer.

In a study of 800 patients with metastatic colorectal cancer, bevacizumab administered intravenously along with IFL extended survival by about 5 months longer than IFL alone. Common side effects of bevacizumab include nosebleeds, fatigue, diarrhea, and high blood pressure. Less common side effects include stroke, heart attacks, angina, and formation of holes in the colon and stomach (gastrointestinal perforation).

Cetuximab. Cetuximab (Erbitux) was approved in February 2004 for the treatment of metastatic colorectal cancer. This monoclonal antibody drug targets epidermal growth factor receptor (EGFR), a protein required by cancer cells in order to proliferate. It can be used either in combination with irinotecan or alone for patients who have not responded to irinotecan. Studies of the cetuximab-irinotecan combination suggest it can help in tumor shrinkage. It has a modest effect on survival, prolonging patients lives by about an additional month.

Panitumumab. Panitumumab (Vectibix) was approved in September 2006 for treatment of colorectal cancer that has metastasized following standard chemotherapy. Like cetuximab, panitumumab is a monoclonal antibody drug that targets EGFR. In clinical trials, panitumumab helped delay disease progression and prolong survival by about 3 months. About 8% of patients experienced tumor shrinkage. Common side effects of this drug include skin rash, fatigue, abdominal pain, nausea, and diarrhea or constipation. Serious side effects include pulmonary fibrosis, severe skin rash, and skin reactions at the infusion site.

Investigational Biologic Drugs

One of the most promising recent developments in cancer treatment research has been the emergence of so-called "targeted therapies." Traditional chemotherapy drugs can be effective, but because they do not distinguish between healthy and cancerous cells their generalized toxicity can cause severe side effects. Targeted therapies work on a molecular level by blocking specific mechanisms associated with cancer cell growth and division. Because they selectively target cancerous cells, they may induce less severe side effects. In addition, these drugs hold the promise of creating options for more individualized cancer treatment based on a patient's genotype. In the future, diagnostic tests may help doctors identify which patients are more likely to respond successfully to specific drugs.

Biologic therapies use the body's immune system to attack the cancer (immunotherapy). These drugs are derived from biological sources and include vaccines, monoclonal antibodies (MAbs), and gene therapies. Many targeted therapies are classified as biologics. Bevacizumab (Avastin), cetixumab (Erbitux), and panitumumab (Vectibix) are currently the three biologic drugs approved for colorectal cancer treatment, but many other drugs are in development.

Targeted therapies involve many different types of drugs and molecular pathways. These include:

Angiogenesis Inhibitors. Anti-angiogenesis drugs inhibit the formation of new blood vessels that supply tumors with the blood, oxygen, and nutrients vital to tumor growth. Angiogenesis inhibitors, such as the monoclonal antibody bevacizumab (Avastin), target vascular endothelial growth factor (VEGF). Cediranib (Recentin), formerly AZD2171, is a new angiogenesis inhibitor that is in Phase III clinical trials for treatment of colorectal cancer.

Tumor Growth Factor Inhibitors. Tumor growth factors, such as epidermal growth factor, stimulate cell growth. Cetixumab (Erbitux) and panitumumab (Vectibix) are the two currently approved colorectal cancer drugs that target the epidermal growth factor receptor (EGFR). Nimotuzumab (TheraCIM) is currently being studied in combination with irinotecan in Phase III trials.

Tyrosine Kinase Inhibitors. Tyrosine kinase is an enzyme associated with EGFR that is involved with the signaling mechanisms that prompt cell growth. The EGFR/tyrosine kinase inhibitor erlotinib (Tarceva), which is approved for the treatment of pancreatic and lung cancers, is being investigated as an adjuvant treatment for metastatic colorectal cancer. Sunitinib (Sutent), which is approved for renal cell carcinoma, is another tyrosine kinase inhibitor in Phase III trials for colorectal cancer.

Radiation Treatment

Radiation therapy uses x-rays to kill cancer cells that might remain after an operation or to shrink large tumors before an operation so that they can be removed surgically. The object of radiation therapy is to damage the tumor as much as possible without harming surrounding tissues. Radiation may be administered in the following ways:

Externally by an x-ray machine (external beam radiation).
By passing radioactive pellets through thin plastic tubes inserted into the intestine.
By implanting tiny radiation seeds directly into the tumor (brachytherapy).
Computer imaging techniques providing 3-dimensional pictures of the cancerous area are allowing precise targeting of radiation to the tumor.

Postoperative Radiation with Chemotherapy for Rectal Cancer

Postoperative radiation treatment combined with chemotherapy is common practice for patients with rectal cancer in Stages II and III. Such patients are at risk of recurrence both at the site of their original tumor and elsewhere in the body. Although there can be significant long-term side effects, the combination of 5-FU and radiation is still considered standard after surgery.

Preoperative Radiation

The standard procedure in the U.S. is to apply radiation after surgery (postoperative). Pre-operative chemotherapy and radiation, however, are sometimes used to preserve sphincter-muscle function and reduce the chance that a patient will need a colostomy. Furthermore, some studies suggest that the use of radiation before surgery reduces the likelihood of recurrences and may slightly prolong survival in some patients with rectal cancer. (It has no additional advantages, however, if the subsequent surgery does not completely remove the cancerous regions.) Studies comparing preoperative and postoperative chemotherapy and radiation are currently under way.

Intra-Operative Radiotherapy (IORT)

Radiation therapy can also be used during surgery (a procedure called intra-operative radiotherapy). It allows the surgeon to move healthy tissue out of the path of the radiation beam.

Side Effects of Radiation Therapy

Short-term side effects of radiation include:

Diarrhea
Skin irritation around the anus
Incontinence
Fatigue
Bowel movement problems

Longer-term complications may include:

Incontinence
Hip and pelvic fractures
Diarrhea
Increased risk for bowel obstruction

Follow-up Testing

The American Society of Clinical Oncology (ASCO) sets guidelines for follow-up testing to detect recurring cancer after the completion of treatment. The following guidelines are based on ASCOs 2005 updated recommendations.

Physical Examination

Most colorectal cancer recurrences happen within 3 years after surgery. American Society of Clinical Oncology recommends that a colorectal cancer patient sees their doctor for a physical examination every 3 - 6 months for the first 3 years, every 6 months for the fourth and fifth years, and at the doctor's and patient's discretion during subsequent years.

Colonoscopy

Patients should have a colonoscopy 3 years after surgery. If the results are normal, patients should then receive a colonoscopy every 5 years. Some patients with hereditary types of colorectal cancer may need more frequent screenings.

A flexible sigmoidoscopy is recommended every 6 months for 5 years for patients with Stage II or III rectal cancer who did not receive radiation therapy.

Carcinoembryonic Antigen Levels

Carcinoembryonic antigen (CEA) levels should be measured every 3 months after surgery for 3 years in patients with Stage II or III cancer. High CEA levels in the blood may indicate that the cancer has spread to other parts of the body.

Imaging Tests

Patients at high risk for cancer recurrence should receive an annual computerized tomography (CT) scan for the first 3 years after treatment. The CT scan can help determine if cancer has spread to the lungs or liver. Patients who have had rectal cancer, and did not have radiation therapy, should receive a pelvic CT scan. The scan is not recommended for most lower-risk patients with Stage I or II colorectal cancer.

Other Tests

American Society of Clinical Oncology does not recommend other follow-up blood tests such as complete blood count, liver function tests, fecal occult blood tests. There appears to be no additional benefit for these tests.

Treatment for Metastasized Colorectal Cancer

The liver is the most frequent site for colorectal cancers to spread (metastasized). Here, treatments may slow the spread of cancer and even prolong survival. Cure is very rare.

Surgery

When cancer has spread, surgery to remove or bypass obstructions in the intestine may be performed. In these circumstances, surgery is considered palliative in that it may improve symptoms but will not lead to cure. In rare cases, metastatic colon cancer may be cured with surgical removal of tumors in areas to which the cancer has spread, such as the liver, ovaries, and lung. The liver is the most common site of spread. Only selected patients may be eligible for such surgery, but in these patients, 5-year survival has been 25% or higher.

Chemotherapy

Chemotherapy may help improve symptoms and possibly prolong survival in metastasized colorectal cancers. Several investigational drugs are being tested. Doctors are also testing chemotherapy administered directly into the liver -- a treatment called hepatic arterial infusion (HAI). A 2006 study found that hepatic arterial infusion improves survival and quality of life for patients whose cancer has spread to the liver. The study indicated that HAI works better for these patients than chemotherapy delivered intravenously.

Other Techniques

Other investigative techniques used to destroy liver tumors include:

Cryosurgery. This approach freezes the tumor or surrounding tissue.
Embolization. Embolization employs a catheter to deliver substances into the liver that block blood vessels and therefore starve the tumor. Chemotherapy is often administered during this procedure.
Radiation.

For end-stage cancer, hospice care is a compassionate option.

Resources

www.cancer.org -- American Cancer Society
www.cancer.gov -- National Cancer Institute
www.oncolink.org -- OncoLink cancer information
www.asco.org -- American Society of Clinical Oncology
www.plwc.org -- People Living with Cancer
www.nccn.org -- National Comprehensive Cancer Network
www.cancer.gov/clinicaltrials -- Find clinical trials

References

Chan AT, Ogino S, Fuchs CS. Aspirin and the risk of colorectal cancer in relation to the expression of COX-2. N Engl J Med. 2007 May 24;356(21):2131-42.

Cole BF, Baron JA, Sandler RS, Haile RW, Ahnen DJ, Bresalier RS, et al. Folic acid for the prevention of colorectal adenomas: a randomized clinical trial. JAMA. 2007 Jun 6;297(21):2351-9.

Flossmann E, Rothwell PM; British Doctors Aspirin Trial and the UK-TIA AspirinTrial. Effect of aspirin on long-term risk of colorectal cancer: consistent evidencefrom randomised and observational studies. Lancet. 2007 May 12;369(9573):1603-13.

Kerr DJ, Dunn JA, Langman MJ, Smith JL, Midgley RS, Stanley A, et al. Rofecoxib and cardiovascular adverse events in adjuvant treatment of colorectal cancer. N Engl J Med. 2007 Jul 26;357(4):360-9.

Levin TR, Zhao W, Conell C, Seeff LC, Manninen DL, Shapiro JA, Schulman J. Complications of colonoscopy in an integrated health care delivery system. Ann Intern Med. 2006 Dec 19;145(12):880-6.

Meyerhardt JA, Niedzwiecki D, Hollis D, Saltz LB, Hu FB, Mayer RJ, et al. Association of dietary patterns with cancer recurrence and survival in patients with stage III colon cancer. JAMA. 2007 Aug 15;298(7):754-64.

U.S. Preventive Services Task Force. Routine aspirin or nonsteroidal anti-inflammatory drugs for the primary prevention of colorectal cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2007 Mar 6;146(5):361-4.

Veit-Haibach P, Kuehle CA, Beyer T, Stergar H, Kuehl H, Schmidt J, et al. Diagnostic accuracy of colorectal cancer staging with whole-body PET/CT colonography. JAMA. 2006 Dec 6;296(21):2590-600.

Review Date: 9/8/2007
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.

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Health Topics A-Z

Colon and rectal cancers

Highlights

Introduction

The Gastrointestinal Tract

Esophagus

Stomach

Small Intestine

Large Intestine

Causes

Inherited Genetic Factors

Biochemical Factors Involved in Colon and Rectal Cancers

Inflammatory Bowel Disease

Symptoms

Weight Loss and Changes in Bowel Movements

Rectal Bleeding

Symptoms of Cancers in Specific Areas of the Colon

Risk Factors

Sex

Age

Ethnicity

Family History

Lifestyle Factors

Risk Factors for People with Inflammatory Bowel Disease

Other Risk Factors

Dietary Factors

Fruits, Vegetables, and Whole Grains

Fats and Oils

Meat and High-Temperature Cooking

Dairy Products and Calcium

Total Calories and Sugar

Coffee and Tea

Vitamin and Mineral Supplements

Prevention

Exercise

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

5-ASAs

Statins

Estrogen in Women

Diagnosis

General Screening Guidelines

Digital Rectal Examination

Fecal Occult Blood Test

Visualizing the Colon: Colonoscopy, Sigmoidoscopy, and Barium Enema

Genetic Screening

Experimental Screening and Diagnostic Methods

Staging

Staging

Stages of Colorectal Cancer

Tumor Markers

Sentinel Node Biopsy

PET/CT Scans

Prognosis

Survival Rates

Factors in Treatment Success

Surgery

Colectomy

Colostomy

Surgical Treatments for Rectal Cancer

Managing Side Effects and Psychological Repercussions

Medications

Chemotherapy Drugs and Regimens

Specific Chemotherapy Drugs

Investigational Biologic Drugs

Radiation Treatment

Postoperative Radiation with Chemotherapy for Rectal Cancer

Preoperative Radiation

Intra-Operative Radiotherapy (IORT)

Side Effects of Radiation Therapy

Follow-up Testing

Physical Examination

Colonoscopy

Carcinoembryonic Antigen Levels

Imaging Tests

Other Tests

Treatment for Metastasized Colorectal Cancer

Surgery

Chemotherapy

Other Techniques

Resources