In the U.S. about 1 in 4 people die from some sort of cancer; 8% of them are from Colon Cancer. The colon, including the rectum, is the final part of our large intestine (see Diagram — Gastrointestinal System). It’s more common with older age, and quite rare under 40; also more common among men. People with an immediate family history of colon cancer (parent, sibling or child), or with certain diseases (Inflammatory Bowel Disease and other uncommon ones), are also at increased risk. Colon Cancer is significantly more common among Blacks then Whites.
Lifestyle factors are implicated in colon cancer, such as low-fiber diets, sedentary lifestyle, obesity, and smoking. These do not change screening recommendations (see below).
Symptoms of Colon Cancer include blood in stools; black tarry stools (“melena;” though also caused by taking iron or Pepto-Bismol®), alternating diarrhea and constipation, or any change in bowel habits; new unusual abdominal pain (this would mean late cancer). Sometimes we find anemia on a routine lab test (CBC) done for other reasons, which leads us to look for cancer. Unfortunately, when symptoms develop, the disease is usually somewhat advanced. Metastatic colon cancer (spread to other organs, mainly the liver, lungs, or abdomen) is the first sign in 20% of people.
Diagnosis of colon cancer is made by colonoscopy. Biopsies show it.
Colon Cancer grows slowly, making it an ideal cancer to screen for. If we find it early enugh, there’s an excellent chance for cure. We should certainly screen for Colon Cancer for anybody:
- Over 50 years-old (or now some say >45, especially for Blacks);
- Had a parent or sibling who had colon cancer at an age 10-years-or less older than patient;
- Persons with Inflammatory Bowel Disease or some uncommon conditions
Screening can be done by colonoscopy, by stool testing in various ways, or by “virtual colonoscopy” (special CT Scan; see colonoscopy link). The latter two require subsequent colonoscopy if abnormal. One advantage of colonoscopy is that it can find and remove polyps which can evolve into cancer, so in that sense the test serves not only to detect the disease, but also to prevent it.