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, such as lymphoma, carcinoid tumors, melanoma, and sarcomas. These are rare. In this article, use of the term “colon cancer” refers to colon carcinoma only.
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 can often lead to a complete cure.
Almost all colon cancer starts 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 higher risk for colon cancer if you:
Certain genetic syndromes 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 associated with a high-fat, low-fiber diet and red meat. However, some studies 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, 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 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, 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.
Imaging tests to screen for and potentially diagnose colorectal cancer include:
Note: Only colonoscopy can see the entire colon, and this is the best screening test for colon cancer.
Blood tests that may be done include:
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: Very early cancer on the innermost layer of the intestine
Stage I: Cancer is in the inner layers of the colon
Stage II: Cancer has spread through the muscle wall of the colon
Stage III: Cancer has spread to the lymph nodes
Stage IV: Cancer has spread to other organs
Blood tests to detect tumor markers, including carcinoembryonic antigen (CEA) and CA 19-9, may help your physician follow you during and after treatment.
Content provided by U.S. National Library of Medicine
A colonoscopy is the gold standard test for colorectal cancer screening. The U.S. Preventive Services Task Force recommends that adults age 50 to 75 be screened for colorectal cancer. Earlier if medically indicated.
