Aug. 13 2010

Is Colonoscopy the Right Tool for Colon Cancer Screening?

Stronger evidence base is needed for choosing colonoscopy over other tools such as sigmoidoscopy, according to recent JAMA article

Over the past decade, colonoscopy has become the standard tool for screening for colon cancer. The American Cancer Society recommends that all Americans be regularly screened, for colon cancer beginning at age 50. Colorectal cancer is the second leading cause of cancer deaths in American men and women.

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Dr. Alfred I. Neugut

In a new commentary in The Journal of the American Medical Association (JAMA), experts at Columbia University’s Mailman School of Public Health and Columbia University Medical Center raise questions about whether colonoscopies are, in fact, better at preventing deaths from colon cancer than other methods. The commentary follows three recent studies that suggest that colonoscopy is no more effective than sigmoidoscopy, an earlier, less costly and less intrusive screening tool with fewer complications.

“Over 20 years have passed since we first started suggesting colonoscopy for screening, and we still don’t have adequate data to back the long-held belief that it is superior to other methods,” says the commentary’s co-author Alfred Neugut, MD, the Myron M. Studner Professor of Cancer Research at Columbia’s College of Physician and Surgeons and professor of epidemiology at the Mailman School of Public Health.

The authors note that questions emerging about colonoscopy are part of a larger re-examination of the efficacy and cost-benefit trade-offs shaking up the field of cancer screening.

“Long-standing recommendations on screening for breast, cervical and prostate cancer have all been questioned based on either new data or re-analyses of older data,” they write in the JAMA commentary. “A similar controversy is also emerging for colorectal cancer screening.”

Before colonoscopy became widely available in the late 1990s, physicians used a procedure called sigmoidoscopy. The methods are similar. Both use a flexible endoscope that is inserted into the colon to look for cancer and pre-cancerous polyps. The difference lies in the length of the scope: a sigmoidoscope only examines the left side of the colon, while a colonoscope can inspect the entire colon.

It seemed only logical that the greater reach of the colonoscope would make it the more effective tool, especially since doctors were detecting increased rates of cancer on the right side of the colon. The American College of Gastroenterology considers colonoscopy to be the preferred screening procedure.

“There used to be a saying that getting a sigmoidoscopy is like getting a mammogram on one breast,” says Benjamin Lebwohl, MD, a gastroenterologist at Columbia University Medical Center and co-author of the JAMA commentary.

But two recent studies in Canada and one in Germany indicate that colonoscopy reduces colon cancer mortality by 40 percent—about the same amount as sigmoidoscopy. More surprisingly, the studies found that colonoscopy did not reduce mortality from right-sided colon cancers.

 “We now have three studies that show colonoscopy gives you the same overall results as sigmoidoscopy with no apparent benefit on the right side,” Dr. Lebwohl says. “The data so far are not living up to the high hopes we have for colonoscopy.”

Still, the authors would like to see confirmation from a U.S. study. Dr. Lebwohl notes that all three studies were conducted in Canada or Europe, where most colonoscopies are performed by primary practitioners. In the U.S., about 75 percent of colonoscopies are performed by gastroenterologists, who have special training to guide the scope around several bends in the colon.

However, the authors also point out that colonoscopies have several disadvantages: They require sedation and the use of an arduous bowel preparation procedure and, while generally safe, they present a higher risk of bowel perforation than sigmoidoscopy.  In addition, colonoscopy is much more expensive.

None of this means that people should stop having colonoscopies. Rather, colonoscopy should not be considered the preferred technique, the authors say. They suggest that sigmoidoscopy should no longer be considered “nonpreferred” and should be more widely offered—at least until additional research provides a stronger evidence base for choosing colonoscopy.

About the Mailman School of Public Health

The only accredited school of public health in New York City and among the first in the nation, Columbia University’s Mailman School of Public Health pursues an agenda of research, education, and service to address the critical and complex public health issues affecting millions of people locally and globally. The Mailman School is the recipient of some of the largest government and private grants in Columbia University’s history. Its more than 1000 graduate students pursue master’s and doctoral degrees, and the School’s 300 multi-disciplinary faculty members work in more than 100 countries around the world, addressing such issues as infectious and chronic diseases, health promotion and disease prevention, environmental health, maternal and child health, health over the life course, health policy, and public health preparedness.

Columbia University Medical Center

provides international leadership in basic, pre-clinical and clinical research, in medical and health sciences education, and in patient care. The medical center trains future leaders and includes the dedicated work of many physicians, scientists, public health professionals, dentists, and nurses at the College of Physicians and Surgeons, the Mailman School of Public Health, the College of Dental Medicine, the School of Nursing, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. Established in 1767, Columbia’s College of Physicians and Surgeons was the first institution in the country to grant the M.D. degree and is now among the most selective medical schools in the country. Columbia University Medical Center is home to the most comprehensive medical research enterprise in New York City and State and one of the largest in the United States. Columbia University Medical Center is affiliated with NewYork-Presbyterian Hospital, the nation’s largest not-for-profit, non-sectarian hospital provider. For more information, please visit www.cumc.columbia.edu.