(Undated) Credit: Photos.com

Colonoscopy, for 20 years a recommended form of screening to catch precancerous polyps, appears no better at helping to reduce deaths from colorectal cancer than a less invasive test, say researchers in Manhattan who are calling for more extensive study of the two techniques.

Drs. Alfred Neugut and Benjamin Lebwohl of Columbia University's public health school say there is no evidence to prove colonoscopy, which allows physicians to visualize the entire 2-foot length of the large intestine, is any more effective at helping doctors find polyps than sigmoidoscopy, which inspects only the lower third.

Citing their review of studies involving hundreds of patients abroad, the researchers say colonoscopy reduces overall colon cancer deaths by only 40 percent, the same as sigmoidoscopy - another form of cancer screening that is less expensive and less invasive. Although sigmoidoscopy uses a flexible tube with camera attachment, it inspects only the lower third of the colon; anesthesia is unnecessary.

Neugut and Lebwohl's analysis showed colonoscopy did not reduce mortality from right-sided colon cancers, the area of the colon that can't be seen by sigmoidoscopy.

Many doctors defended colonoscopies' effectiveness. "A sigmoidoscopy only examines the last third of the colon," said Dr. Luz P. Angel, a colorectal surgeon at North Shore-Long Island Jewish Health System. "That's like getting a mammogram on one breast."

Angel said she viewed colonoscopy as "the best way to find polyps and prevent colon cancer," though she noted sigmoidoscopy is simpler and less expensive. "I think the motivation of research like this is to reduce health care costs," she said.

A sigmoidoscopy at North Shore University Hospital in Manhasset costs $250, Angel said. A colonoscopy costs $500, but an additional $500 is charged for the anesthesia.

Some health policy experts say analysis such as the kind carried out at Columbia serves as a cue to the insurance industry that patients can fare just as well with a less expensive examination.

Lebwohl Tuesday insisted saving money was not the intent of their report, published in Wednesday's Journal of the American Medical Association. They want to urge better research into the benefits and drawbacks of colonoscopy, he said.

U.S. doctors note colonoscopy is performed by general-practice physicians overseas, and that they may lack the expertise of highly trained specialists. In the United States, colonoscopies are performed by gastroenterologists.

The analysis, however, comes at a time when critics are questioning a range of cancer screening techniques, weighing their efficacy and cost. Medical policy experts have questioned mammography and PSA screening for prostate cancer. Although colonoscopy has the benefit of catching precancerous polyps, it is not risk free, experts say, and can occasionally result in perforation of the colon.

"From our professional experience, doing thousands of colonoscopies, we see multiple right-sided colon polyps that would have been missed with a sigmoidoscopy," said Dr. Chris Lascarides, a cancer specialist at Stony Brook University Medical Center.

Dr. Clare Bradley, chief medical officer for the American Cancer Society's eastern division, said her organization recommends either technique: A colonoscopy from age 50 and every 10 years thereafter when a test is normal, or sigmoidoscopy repeated every five years when no abnormalities are found. Bradley said she personally would still opt for colonoscopy.

Latest videos