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Study Finds Colonoscopy Best Choice for Screening

Breaking News - May 2005 - Week 4

(May 25, 2005)

Healthcare in  the News

-- Colonoscopy is the best test to catch colon cancer early in women, according to a report in the New England Journal of Medicine.

A picture of a woman standing outside.

Colonoscopy, in which the entire colon is examined, finds more precancerous polyps than does flexible sigmoidoscopy, which reaches only the lower quarter of the colon, researchers say.

"This is the first large-scale study in women to assess the efficacy of colonoscopy as a colon cancer screening tool," says study author Dr. Philip Schoenfeld, an assistant professor of gastroenterology at the University of Michigan Medical School, in Ann Arbor.

"While fecal occult blood testing and flexible sigmoidoscopy are less expensive, faster, and require no sedation, 65 percent of women with advanced precancerous polyps in our study would have lesions missed if these were the only screening tests performed because precancerous polyps are found deeper in the colon in women," Dr. Schoenfeld reports.

Colorectal cancer is the third most common cancer in the US, according to the American Cancer Society (ACS). About 104,950 new cases of colon cancer and 40,340 new cases of rectal cancer will be diagnosed in 2005, the ACS estimates. About 56,290 deaths in total are expected from both malignancies this year.

Differs from Findings with Men

Dr. Schoenfeld's team evaluated 1,463 women, ages 50 to 79, including 230 with a family history of colon cancer. The physicians performed colonoscopy on each one and found it detected advanced polyps - considered a precursor to cancer - in 72 of the women, or 4.9 percent. They also noted the location of the polyps.

Then the "diagnostic yield" of sigmoidoscopy was calculated by estimating the proportion of patients whose lesions would have been identified if they had that test alone. The lesions were considered detectable if they were found in the parts examined by a sigmoidoscopy.

The team compared the findings with results from another study called the Veterans Administration Cooperative Study 380, which evaluated more than 3,000 patients, 97 percent of them men.

The VA study had found that fecal occult blood testing (which detects microscopic amounts of blood in the stool) and sigmoidoscopy would identify more than 70 percent of men with advanced polyps.

Not so for women, however, Dr. Schoenfeld's team finds. While colonoscopy found advanced polyps in 4.9 percent of the women, sigmoidoscopy alone would have found polyps in only 1.7 percent of the women, and missed them in 3.2 percent.

Only 35.2 percent of women with advanced polyps would have had their lesions identified if they had undergone just sigmoidoscopy, as compared with 66.3 percent of the men matched for age from the VA study.

The ACS recommends men and women at average risk begin to be screened at age 50, using either blood stool tests annually, sigmoidoscopy every five years, annual blood stool tests plus sigmoidoscopy every five years, double contrast barium enema every five years, or colonoscopy every 10 years.

Leading Experts Lend Perspective

In response to the new research, the ACS program director of the prostate and colorectal cancer control department, Dr. Durado D. Brooks, says, "This is an important and somewhat concerning study. It is important to keep in mind that the total number of women who had what the researchers called advanced neoplasia - polyps that have a cancerous potential - was very small (72 out of 1463 women). It would be good to see corroboration of these findings in other studies."

He adds, however, that "if these findings are supported - that flexible sigmoidoscopy in women will miss up to two-thirds of significant findings in the proximal colon - that certainly would impact future recommendations by the American Cancer Society and others.

"For now, the Society recommends men and women should talk to their doctors and learn the facts about all colorectal cancer screening options and make an informed decision about which test is most appropriate for them," Dr. Brooks says.

Dr. Schoenfeld notes, "These data reinforce two key points - that colonoscopy is clearly the preferred colorectal cancer screening tool in women. And we need to remember that we can't take medical research studies that have been done in men and apply those to women."

Dr. Donald David, director of the department of gastroenterology at the City of Hope National Medical Center, in Duarte, Calif., says the study results are not surprising.

"We always thought colonoscopy was the best test for colon cancer screening," he says. "What we do see yet again is that colonoscopy is the only test that makes sense."

Dr. David predicts a trend toward using colonoscopy and dropping sigmoidoscopy. He adds he is currently reviewing screening guidelines for a national cancer network, and will recommend that change.

Always consult your physician for more information.

For more information on health and wellness, please visit health information modules on this Web site.

ACS: Colonoscopy Explained

According to the American Cancer Society (ACS), a colonoscope is a longer version of a sigmoidoscope. It is inserted through the rectum and allows a physician to see the lining of your entire colon.

The colonoscope is also connected to a video camera and display monitor so a physician can closely examine the inside of the colon.

If a small polyp is found, your physician may remove it, the ACS states.

Polyps, even those that are not cancerous, can eventually become cancerous. For this reason, they are usually removed.

This is done by passing a wire loop through the colonoscope to cut the polyp from the wall of the colon with an electrical current.

The polyp can then be sent to a lab to be checked under a microscope to see if it has any areas that have changed into cancer.

If your physician sees a large polyp or tumor or anything else abnormal, a biopsy will be done, states the ACS.

In this procedure, a small piece of tissue is taken out through the colonoscope. Examination of the tissue can help determine if it is a cancer, a benign (non-cancerous) growth, or a result of inflammation.

If you have a colonoscopy, you will need to follow a clear-liquid diet and take laxatives the day before the test and an enema that morning to clean your colon so no stool will block the view.

Colonoscopy can be uncomfortable. To avoid this, you will be given a sedating medication through a vein to make you feel relaxed and sleepy during the procedure.

Colonoscopy may be done in a hospital outpatient department or ambulatory care center and usually takes 15 to 30 minutes, although it may take longer if polyp removal is involved.

Always consult your physician for a diagnosis.

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