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Melanie Munk, Features Editor munk@heraldnet.com

Cancer findings renew benefits of colon tests

Dr. Elizabeth Smoots
Herald Columnist

New developments are happening in the field of colorectal cancer. Just this month, scientists announced a surprising discovery about the second-leading cause of U.S. cancer deaths. At the same time, experts released the first-ever joint consensus guidelines for colorectal cancer screening. Then there's the hoopla surrounding National Colorectal Awareness Month in March. Put that all together and what do you get?

A lot of excitement about colon cancer. And a good opportunity to learn something new about it. Let's start with these top questions.

How does it develop?

It usually evolves from fingerlike projections in the lining of the colon, called polyps. Scientists blame most colorectal cancer on these growths. But this may not be the whole story, recent research reveals. A team of researchers has found that some cancers spring from flat growths or shallow potholes in the colon's lining.

The study looked at 1,800 participants -- mostly men -- at a large hospital for military veterans in Palo Alto, Calif. Researchers used colonoscopy to find tumors during the study. In this procedure, a doctor guides a lighted tube with a magnifying lens on the end, inserted at the rectum, through much of the length of the colon.

Using a special dye to make tumors easier to see, researchers found that flat or depressed growths comprised about 15 percent of all benign and malignant tumors that were detected. But more than half of the malignant tumors, or cancers, were found in the flat growths.

Overall, researchers found that flat growths were nearly 10 times more likely to contain cancer cells compared to tumors shaped like a polyp. This makes flat growths less common but more risky, concluded the researchers.

What's best detection?

The American Cancer Society and several other organizations just released joint consensus guidelines for colorectal screening. The guidelines are based on the best scientific evidence currently available.

The overriding goal of the guideline is to detect precancerous growths or colorectal cancer early -- before symptoms arise -- when they're most curable. To do this, beginning at age 50, adults at average risk for colon cancer should get one of the following recommended periodic tests:

Colonoscopy every 10 years, or

Flexible sigmoidoscopy every five years, or

Double contrast barium enema every five years, or

CT colonography every five years

High-risk individuals also need testing, usually more often and earlier. Additional ways to catch cancer early include stool occult-blood tests, stool immunochemical tests and a new stool DNA test that looks for genetic evidence of cancer.

Flat growth detection

Flat or pothole-shaped growths are harder to detect with most current tests compared to polyps. Special dyes -- not commonly available -- may be required. But I suspect that research to further refine cancer screening tests will soon be in the works.

In an editorial accompanying the Palo Alto research, published in the Journal of the American Medical Association, Dr. David Lieberman said: "Imaging tests such as computed tomography colonography are unlikely to detect flat lesions, which do not protrude into the lumen of the colon." Imaging tests include CT colonography, also called "virtual colonography," and double contrast barium enema. Lieberman is a professor of gastroenterology at Oregon Health and Science University in Portland.

If you opt for colonoscopy or sigmoidoscopy, having a high-quality examination is very important, Lieberman stressed. For patients, that means finding a skilled doctor and carefully following stool clean-out instructions before the procedure.

For more information: Prevent Cancer Foundation, www.preventcancer.org.

Contact Dr. Elizabeth Smoots, a board-certified family physician and fellow of the American Academy of Family Physicians, at doctor@practicalprevention.com. Her columns are not intended as a substitute for medical advice or treatment. Before adhering to any recommendations in this column consult your health care provider.

© 2008 Elizabeth S. Smoots