Virtually all colon cancer develops from adenomatous polyps in the colon, generally referred to simply as colon polyps. A personal or family history of polyps puts you at higher risk for colon cancer.
Personal History of Colon Polyps
Polyps don't always become cancerous, but your risk of developing cancer increases with the number and size of colon polyps you have. Approximately one percent of polyps with a diameter less than a centimeter are cancerous. If you have one little polyp that size, the American Cancer Society (ACS) recommends that the doctor remove it and that you receive another colonoscopy three to six years later. (Without any polyps, the due date would've been ten years later.)
If you have more than one polyp or the polyp is bigger than a centimeter, you're considered at even higher risk for colon cancer. After your colon polyps are removed, you'll probably be asked to get another colonoscopy in three years. The doctor may also test the polyp since up to 50 percent of polyps greater than two centimeters (about the diameter of a nickel) are cancerous.
Family History of Colon Polyps
When it comes to polyps and colon cancer risk, family history is important. It's probably not the most comfortable conversation to have, but you should find out if your parents, siblings, or children have ever had any colon polyps. If they have, you're not in the average-risk category for colon cancer anymore.
If two or more first-degree relatives have had colon polyps, the ACS recommends that you receive your first colonoscopy at age 40 or ten years before the age when your relative's polyp was found, whichever is earlier. Both of my parents have had polyps, so I'll be getting a colonoscopy when I'm 40 instead of when I'm 50.
Another family scenario that would increase your risk is if one first-degree relative had a colon polyp before age 60. So, one parent with a polyp or one sibling with a polyp. The same higher-risk recommendations apply. If your brother had a polyp removed when he was 45, the ACS says you should get a colonoscopy when you're 35.
To learn about other causes of colorectal cancer, please read Fifteen Causes of Colon Cancer.
You may also want to take a look at the Polyp Size Gallery, which is designed to let you see what polyps look like and how big they are in real life. Looking at them this way helps demonstrate why you can't count on noticing that a polyp is present.Sources:
- Buetow, P. and Buck, J. "Colorectal Adenocarcinoma." RadioGraphics 15.1 (Jan. 1995). 28 Aug. 2006 [http://www.rsna.org/REG/publications/rg/afip/privateM/1995/0015/0001/0127/1.htm#topAnchor].
- Detailed Guide: Colon and Rectum Cancer: What Are the Risk Factors for Colorectal Cancer? American Cancer Society. 7 Mar. 2006. 28 Aug. 2006 [http://www.cancer.org/docroot/CRI/content/CRI_2_4_2X_What_are_the_risk_factors_for_colon_and_rectum_cancer.asp].