Colon Cancer

Colon cancer is cancer that starts in the large intestine (the colon), which is the lower part of your digestive system. Rectal cancer is cancer of the last several inches of the colon. These cancers are similar and, together, they are often referred to as colorectal cancers.

The colon and the rectum are parts of the large intestine, which is the lower part of the body’s digestive system. During digestion, food moves through the stomach and small intestine into the colon. The colon absorbs water and nutrients from the food and stores waste matter (stool). Stool moves from the colon into the rectum before it leaves the body.

Most cases of colon cancer begin as small, noncancerous (benign) clumps of cells called adenomatous polyps. Over time some of these polyps become colon cancers.

Polyps may be small and produce few, if any, symptoms. For this reason, doctors recommend regular screening tests to help prevent colon cancer by identifying polyps before they become colon cancer.

Many cases of colon cancer have no symptoms. If symptoms are present, they may include abdominal pain and tenderness in the lower abdomen, blood in the stool, diarrhea, constipation or other changed in bowel habits, and weight loss for no known reason.

Colorectal cancer is the third most common type of cancer in men and women in the United States. It is a leading cause of cancer death, but deaths from colorectal cancers have decreased in recent years with the widespread use of regular screenings, including colonoscopies and fecal occult blood tests, which check for blood in the stool.

In most cases, the cause of colon cancer is not clear. Doctors know that colon cancer occurs when healthy cells in the colon become altered. Healthy cells grow and divide in an orderly way to keep your body functioning normally. But when a cell is damaged and becomes cancerous, cells continue to divide, even when new cells are not needed. These cancer cells can invade and destroy normal tissue nearby, and cancerous cells can travel to other parts of the body.

Colon cancer most often begins as clumps of precancerous cells (polyps) on the inside lining of the colon. Polyps can appear mushroom-shaped, or they can be flat or recessed into the wall of the colon. Removing polyps before they become cancerous can prevent colon cancer.

Inherited gene mutations that increase the risk of colon cancer can be passed through families, but these inherited genes are linked to only a small percentage of colon cancers. Inherited gene mutations do not make cancer inevitable, but they can increase an individual's risk of developing cancer.

Factors that may increase your risk of colon cancer include:

• Older age. Most people diagnosed with colon cancer are older than 50 years. Colon cancer can occur in younger people, but it occurs much less frequently.
• African-American race. African-Americans have a greater risk of colon cancer than do people of other races.
• A personal history of colorectal cancer or polyps. If you have already had colon cancer or adenomatous polyps, you have a greater risk of colon cancer in the future.
• Inflammatory intestinal conditions. Chronic inflammatory diseases of the colon, such as ulcerative colitis and Crohn's disease, can increase your risk of colon cancer.
• Inherited syndromes that increase colon cancer risk. Genetic syndromes passed through generations of your family can increase your risk of colon cancer. These syndromes include familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, which is also known as Lynch syndrome.
• Family history of colon cancer and colon polyps. You are more likely to develop colon cancer if you have a parent, sibling, or child with the disease. If more than one family member has colon cancer or rectal cancer, your risk is even greater. In some cases, this connection may not be hereditary or genetic. Instead, cancers within the same family may result from shared exposure to an environmental carcinogen or from diet or lifestyle factors.
• Low-fiber, high-fat diet. Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories. Some studies have found an increased risk of colon cancer in people who eat diets high in red meat. Diets high in vegetables, fruits, and whole grains have been linked with a decreased risk of colorectal cancer, but fiber supplements do not seem to help. It is not clear if other dietary components (for example, certain types of fats) affect colorectal cancer risk.
• A sedentary lifestyle. If you are inactive, you are more likely to develop colon cancer. Getting regular physical activity may reduce your risk of colon cancer.
• Diabetes. People with diabetes and insulin resistance may have an increased risk of colon cancer.
• Obesity. People who are very overweight or obese have an increased risk of colon cancer and an increased risk of dying of colon cancer when compared with people considered normal weight.
• Smoking. People who smoke cigarettes may have an increased risk of colon cancer.
• Alcohol. Heavy use of alcohol may increase your risk of colon cancer.
• Radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colon cancer.

See your doctor for lasting changes in bowel habits, blood in the stool, ongoing abdominal discomfort, or unexplained weight loss, and keep up with recommended colon-cancer screening. Early detection greatly improves outcomes.