Colon cancer is result of both behavior, genes

DEAR DOCTOR K: During a screening colonoscopy, my doctor found a polyp in my colon. Does this mean I have cancer?

DEAR READER: Colon polyps are common, non- cancerous growths of tissue inside the colon, or large intestine. Some of them are benign. However, other colon polyps can progress into colon cancer. These are called adenomatous polyps.

Overall, only a small percentage of adenomas progress to cancer, but it's not currently possible to accurately predict which ones will do so. So generally they are removed.

Adenomatous polyps progress to cancer as the result of changes in certain genes inside the cells of the polyp. ( I've put an illustration of how a polyp can turn into cancer on my website, AskDoctorK. com.) Every human cell has certain genes that, when turned on, can cause the cell to start multiplying uncontrollably. Fortunately, those " oncogenes" are generally turned off. Our cells also have certain tumor- suppressor genes that stop a cell from multiplying uncontrollably. Also fortunately, those genes generally are turned on.

A colonoscopy is designed to find growths on the colon wall before they have a chance to turn into cancer. During this screening test, your doctor inspects your colon with a colonoscope -- a thin, lighted, flexible tube fitted with a video camera.

A colonoscope can also grab and snip off any small polyps it encounters. ( If a polyp is larger, surgery may be required to remove it.)

If a polyp is not removed, it will continue to grow larger and possibly become cancerous. The larger the polyp, the greater the chance it contains cancerous cells. However, it usually takes several years for a polyp to change to a cancer.

People with one adenomatous polyp are at greater risk for developing others. In fact, it is not unusual for more than one adenomatous polyp to be discovered during a single colonoscopy. So if you had an adenomatous polyp, you were probably advised to get another colonoscopy in two to five years.

How soon you need to return depends largely on the size of the polyps found in the first exam. If no adenomatous polyps are found, generally a repeat colonoscopy is recommended in seven to 10 years.

In the meantime, certain steps may help lower your risk of colon cancer:

-- Eat less meat. Eat minimal red meat -- especially processed or cured meats.

-- Follow a healthy diet. Increase your consumption of fruits, vegetables and whole grains.

-- Maintain a healthy weight. Extra fat, especially around the waist, increases your chances of developing colon cancer.

-- Don't smoke. Smoking increases the risk of colon cancer.

You may sense a contradiction. I said that colon cancer is the result of certain genetic changes -- but I also said that it is caused by behavior ( eating red meat, smoking, becoming overweight). So which is it?

It's both. The behaviors affect the genes. They produce mutations in the genes, causing them to be inappropriately turned on and off. You should do everything you can to minimize your risk for this cancer.