December 16th, 2008
03:07 PM ET

Colon cancer screening confusion

By Miriam Falco
CNN Medical Managing Editor

In a study published this week in the Annals of Internal Medicine, Canadian researchers found that colonoscopies, the procedure used by doctors to examine the colon for abnormalities and growths, is useful for finding cancer or pre-cancerous growths in the left side of the colon, but not so useful at finding them in the right side of the colon.

Now I’ve done a lot of stories on colon cancer and colonoscopies, but left and right sides of the colon haven’t come up that often.

Researchers think that colonoscopies may not detect as many cancers in the right, or “ascending” part of the colon because it’s the farthest region to reach with the probe, making it difficult to access.

But when I first read the study I wondered what people will think when they read the study results? Possibly that colonoscopies don’t work?

And the story headlines confirm my hunch:

“Colonoscopy Screenings May Not Be That Accurate”
“Colonoscopies Prevent Fewer Cancer Deaths Than Thought in Study”
“Colonoscopy saves lives, but study finds flaws”
“Colonoscopies miss many cancers, study finds”

It’s important to understand that colonoscopies are a screening tool, meant to detect the earliest signs of cancer. Having the screening at the recommended age of 50 can locate and remove pre-cancerous polyps, preventing the development of cancer. But, like other screening tools, the procedure isn’t perfect.

The accompanying editorial suggests doctors may mislead patients into thinking that the screening reduces the risk of colorectal cancer death by 90 percent, when it’s closer to 60 or 70 percent. The American Cancer Society told me that they conservatively say colonoscopies reduce the risk for colorectal cancer by about 50 percent.

I spoke with Dr. Hal Sox, editor of the journal, to get clarity on the message they are trying to send. Sox said the message is not to discourage people from getting a colonoscopy, but to stress that it’s not a perfect screening tool. A clean colonoscopy doesn’t mean that people who have other symptoms, such as blood in the stool, shouldn’t have themselves checked by a doctor.

Colorectal cancer is the third most commonly diagnosed cancer and the third-leading cause of cancer death in both men and women in the United States. Getting screened and finding polyps or tumors early saves lives.

Have you had a colonoscopy? If not, why?

Editor's Note: Medical news is a popular but sensitive subject rooted in science. We receive many comments on this blog each day; not all are posted. Our hope is that much will be learned from the sharing of useful information and personal experiences based on the medical and health topics of the blog. We encourage you to focus your comments on those medical and health topics and we appreciate your input. Thank you for your participation.

About this blog

Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.