Reviewed By David Zieve MD, MHA, Medical Director, A.D.A.M., Inc., and Yi-Bin Chen, MD, Leukemia/Bone… Marrow Transplant Program, Massachusetts General Hospital.more »
Definition
Colon, or colorectal, cancer is cancer that starts in the large intestine (colon) or the rectum (end of the colon).
According to the American Cancer Society, colorectal cancer is one of the leading causes of cancer-related deaths in the United States. However, early diagnosis often leads to a complete cure.
Almost all colon cancer starts in glands in the lining of the colon and rectum. When most people and when doctors talk about colorectal cancer, this is generally what they are referring to.
There is no single cause for colon cancer. Nearly all colon cancers begin as noncancerous (benign) polyps, which slowly develop into cancer.
Certain genetic syndromes also increase the risk of developing colon cancer. Two of the most common are hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, and familial adenomatous polyposis (FAP).
What you eat may play a role in your risk of colon cancer. Colon cancer may be associated with a high-fat, low-fiber diet and red meat. However, some studies found that the risk does not drop if you switch to a high-fiber diet, so the cause of the link is not yet clear.
Smoking cigarettes and drinking alcohol are other risk factors for colorectal cancer.
Symptoms
Many cases of colon cancer have no symptoms. The following symptoms, however, may indicate colon cancer:
With proper screening, colon cancer can be detected before symptoms develop, when it is most curable.
Your doctor will perform a physical exam and press on your belly area. The physical exam rarely shows any problems, although the doctor may feel a mass in the abdomen. A rectal exam may reveal a mass in patients with rectal cancer, but not colon cancer.
A fecal occult blood test (FOBT) may detect small amounts of blood in the stool, which could suggest colon cancer. However, this test is often negative in patients with colon cancer. For this reason, a FOBT must be done along with colonoscopy or sigmoidoscopy. It is also important to note that a positive FOBT doesn't necessarily mean you have cancer.
If your doctor learns that you do have colorectal cancer, more tests will be done to see if the cancer has spread. This is called staging. CT or MRI scans of the abdomen, pelvic area, chest, or brain may be used to stage the cancer. Sometimes, PET scans are also used.
Stage 0 colon cancer may be treated by removing the cancer cells, often during a colonoscopy. For stages I, II, and III cancer, more extensive surgery is needed to remove the part of the colon that is cancerous. (See: Colon resection)
There is some debate as to whether patients with stage II colon cancer should receive chemotherapy after surgery. You should discuss this with your oncologist.
Almost all patients with stage III colon cancer should receive chemotherapy after surgery for approximately 6 - 8 months. The chemotherapy drug 5-fluorouracil has been shown to increase the chance of a cure in certain patients.
Chemotherapy is also used to treat patients with stage IV colon cancer to improve symptoms and prolong survival.
Although radiation therapy is occasionally used in patients with colon cancer, it is usually used in combination with chemotherapy for patients with stage III rectal cancer.
Colon cancer is, in many cases, a treatable disease if caught early.
How well you do depends on many things, including the stage of the cancer. In general, when treated at an early stage, the vast majority of patients survive at least 5 years after their diagnosis. (This is called the 5-year survival rate.) However, the 5-year survival rate drops considerably once the cancer has spread.
If the colon cancer does not come back (recur) within 5 years, it is considered cured. Stage I, II, and III cancers are considered potentially curable. In most cases, stage IV cancer is not curable.
The death rate for colon cancer has dropped in the last 15 years. This may be due to increased awareness and screening by colonoscopy.
Colon cancer can almost always be caught in its earliest and most curable stages by colonoscopy. Almost all men and women age 50 and older should have a colon cancer screening. Patients at risk may need screening earlier.
Colon cancer screening can find precancerous polyps. Removing these polyps may prevent colon cancer.
Dietary and lifestyle modifications are important. Some evidence suggests that low-fat and high-fiber diets may reduce your risk of colon cancer.
Several studies have reported that NSAIDs (aspirin, ibuprofen, naproxen, celecoxib) may help reduce the risk of colorectal cancer. However, the U.S. Preventive Services Task Force and the American Cancer Society recommends against taking aspirin or other anti-inflammatory medicines to prevent colon cancer if you have an average risk of the disease -- even if someone in your family has had the condition. Taking more than 300 mg a day of aspirin and similar drugs may cause dangerous gastrointestinal bleeding and heart problems in some people.
Although low-dose aspirin may help reduce your risk of other conditions, such as heart disease, it does not lower the rate of colon cancer.
References
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Colon Cancer. V3.2009.
Cuzick J, Otto F, Baron JA, et al. Aspirin and non-steroidal anti-inflammatory drugs for cancer prevention: an international consensus statement. Lancet Oncol. 2009 May;10(5):501-7.
Lieberman DA. Clinical practice. Screening for colorectal cancer. N Engl JMed. 2009 Sep 17;361(12):1179-87.
Cappell MS. Pathophysiology, clinical presentation, and management of colon cancer. Gastroenterol Clin North Am. 2008;37:1-24.
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