The colon is the main part of the large intestine, beginning at the cecum (which connects to the small intestine) and ending at the rectum. Sometimes, small clumps of benign cells, called polyps, form in the lining of the colon or rectum. Over time – usually five to 10 years – the cells in some of these polyps may grow abnormally and develop into colon cancers, also called colorectal cancer.
Not all polyps form into cancer. Inflammatory polyps, for example, do not. A screening is the only way to detect the difference, and screenings have helped reduce the number of cases annually since the mid-1980s, according to the American Cancer Society.
Still, colon cancer is the fourth-most diagnosed cancer, following breast, lung and prostate cancers, with a lifetime risk of one in 23. The earlier the cancer or precancerous polyps are detected, the more successful, and easier, the treatment.
Polyps on their own produce few or no symptoms, and patients in the early stages of colon cancer may not experience warning signs. Once the cancer develops, symptoms might include:
- Changes in bowel movements, including diarrhea, constipation or a change in the shape and/or consistency of the stool.
- Rectal bleeding or blood in the stool.
- Abdominal discomfort, including cramps, gas, or pain.
- Feeling that the bowel doesn’t empty completely.
- Weakness or fatigue
- Unexplained weight loss (without dieting).
Regular screenings are advised to catch and remove polyps before they become cancerous. Typically, the average-risk patient is recommended to start colon cancer screening at age 50, but there is an increasing incidence of colon cancer in young patients and it may be recommended to start earlier if you have symptoms or a family history of polyps or cancer.
- Colonoscopy – A long, flexible tube, equipped with a tiny video camera, is inserted into the colon through the anus. The doctor examines the entire colon for polyps and removes them, if found.
- Sigmoidoscopy – To examine the last two feet of the colon (or descending colon), a flexible tube (sigmoidoscope) is inserted through the anus and provides imaging through a tiny camera.
- Colonography – Air is gently pumped into the colon through a narrow tube, and then a special machine takes 2- and 3-dimension images of the colon and rectum.
- Fecal tests – Often performed at home, these tests screen stool samples for blood to detect early-stage cancer, but not polyps. These are not appropriate for high-risk individuals.
Treatment for colon cancer varies depending on the location and stage of the disease.
Treatments for early-stage colon cancer:
- Removing polyps during a colonoscopy – This approach is effective if the cancer is in an early stage and completely contained within the polyp. Some colon lining also may be taken with larger polyps.
- Laparoscopic surgery – If polyps can’t be removed during a colonoscopy, the surgeon can take them through several small incisions in the abdominal wall, using an instrument with an attached camera.
Treatments for advanced colon cancers:
- Partial colectomy– The surgeon removes the part of the colon that contains the cancer, along with tissue on either side of the cancer.
- Lymph node removal– This procedure is usually performed during colon cancer surgery to test for cancer.
- Chemotherapy – Chemical substances are administered after surgery to shrink large cancers or cancer that has spread to the lymph nodes.