Colon, or colorectal, cancer is cancer that starts in the large intestine (colon) or the rectum (end of the colon).
Other types of cancer can affect the colon. These include lymphoma, carcinoid tumors, melanoma, and sarcomas. These are rare. In this article, colon cancer refers to colon carcinoma only.
Colorectal cancer is one of the leading causes of cancer-related deaths in the United States. Early diagnosis, though, can often lead to a complete cure.
Almost all colon cancers start in glands in the lining of the colon and rectum. When doctors talk about colorectal cancer, this is usually what they are talking about.
There is no single cause of colon cancer. Nearly all colon cancers begin as noncancerous (benign) polyps, which slowly develop into cancer.
You have a high risk of colon cancer if you:
Certain inherited diseases also increase the risk of developing colon cancer. Two of the most common are:
What you eat may play a role in your risk of colon cancer. Colon cancer may be linked to a high-fat, low-fiber diet and to a high intake of red meat. Some studies, though, have found that the risk does not drop if you switch to a high-fiber diet, so this link is not yet clear.
Smoking cigarettes and drinking alcohol are other risk factors for colorectal cancer.
Many cases of colon cancer have no symptoms. The following symptoms may indicate colon cancer:
With screening colon cancer can be detected before symptoms develop. This is when the cancer 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 lump (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. This may suggest colon cancer. FOBT must be done along with colonoscopy or sigmoidoscopy to screen for and diagnose colorectal cancer.
Note: Only colonoscopy can see the entire colon. This is the best screening test for colon cancer.
Blood tests that may be done include:
If you are diagnosed with 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.
Stages of colon cancer are:
Blood tests to detect tumor markers, including carcinoembryonic antigen (CEA) and CA 19-9, may help your physician follow you during and after treatment.
Treatment depends on many things, including stage of the cancer. Treatments may include:
Stage 0 colon cancer may be treated by removing the cancer cells. This is done using colonoscopy. For stages I, II, and III cancer, more extensive surgery is needed to remove the part of the colon that is cancerous. This surgery is called colon resection.
Almost all patients with stage III colon cancer should receive chemotherapy after surgery for 6 - 8 months. This is called adjuvant chemotherapy. The drug 5-fluorouracil can increase the chance of a cure in certain patients.
You may receive just one type, or a combination of these drugs. 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.
Radiation therapy is sometimes used in patients with colon cancer. It is usually used in combination with chemotherapy for patients with stage III rectal cancer.
For patients with stage IV disease that has spread to the liver, treatments directed at the liver can be used. This may include:
In many cases, colon cancer is treatable when it is caught early.
How well you do depends on many things, especially the stage of the cancer. When treated at an early stage, many patientssurvive at least 5 years after diagnosis. This is called the 5-year survival rate.
If the colon cancer does not come back (recur) within 5 years, it is considered cured. Stage I, II, and III cancers are considered possibly curable. In most cases, stage IV cancer is not considered curable, although there are exceptions.
Call your health care provider if you have:
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 by colonoscopy in its earliest and most curable stages. Almost all men and women age 50 and older should have a colon cancer screening. Patients at higher risk may need earlier screening.
Colon cancer screening can often find polyps before they become cancerous. Removing these polyps may prevent colon cancer.
Changing your diet and lifestyle is important. Medical research suggests that low-fat and high-fiber diets may reduce your risk of colon cancer.
Some studies have reported that NSAIDs (aspirin, ibuprofen, naproxen, celecoxib) may help reduce the risk of colorectal cancer. But these medicines can increase your risk of bleeding and heart problems. Your health care provider can tell you more about the risks and benefits of the medicines and other ways that help prevent colorectal cancer.
Cunningham D, Atkin W, Lenz HJ, Lynch HT, Minsky B, Nordlinger B, et al. Colorectal cancer. Lancet. 2010;375:1030-1047.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines): Colon cancer. Version 2.2013. Available at http://www.nccn.org/professionals/physician_gls/pdf/colon.pdf. Accessed November 16, 2012.
Smith RA, Cokkinides V, Brawley OW. Cancer screening in the United States, 2012: a review of current American Cancer Society guidelines and current issues in cancer screening. CA Cancer J Clin. 2012;62:129-142.
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