Physicians appear to be performing surveillance colonoscopies at frequencies higher than those recommended by evidence-based medical guidelines, according to results of a survey conducted by the National Cancer Institute (NCI), part of the National Institutes of Health. Surveillance colonoscopies are follow-up colonoscopies given to patients who already have had a colorectal abnormality detected and removed. These results, which appear in the August 17, 2004, Annals of Internal Medicine*, suggest that as the demand for colonoscopies in the United States increases, overperformance could use up limited physician resources and cause unnecessary risk to patients.

Pauline Mysliwiec, M.D., now at the University of California-Davis School of Medicine, and colleagues, sought to learn how well physicians followed recommended guidelines for surveillance colonoscopies, and what factors most influence a physician’s decisions. The U.S. Preventive Services Task Force (USPSTF)** sets federal government guidelines for preventive disease screenings, based on cost-effectiveness, evidence from scientific research, and clinical trials. Private organizations such as the American Cancer Society also set cancer screening guidelines.

The authors surveyed both gastroenterologists and general surgeons about their opinions and practices regarding the use of surveillance colonoscopy in various clinical scenarios. The aim was to find out how often physicians would recommend a colonoscopy and/or other procedures following an initial discovery of a colorectal abnormality in a healthy and asymptomatic 50-year-old patient. The possible abnormalities included a small, benign, hyperplastic polyp, a single small adenoma, a single large adenoma, or multiple adenomas. A physician could recommend a colonoscopy, fecal occult blood testing, a double-barium enema, flexible sigmoidoscopy, or a general rectal exam.

The study found that both groups of physicians recommended a colonoscopy in a follow-up session at a higher frequency than guidelines would require, especially in situations where the initial findings were considered low-risk. In the lowest risk scenario — a patient diagnosed with only a small, hyperplastic polyp — 24 percent of gastroenterologists and 54 percent of general surgeons recommended a colonoscopy, either alone or in conjunction with another procedure, at a frequency of at least every five years. Medical guidelines do not recommend any follow-up colonoscopy for hyperplastic polyps because the presence of these polyps has not been shown to increase the risk of colorectal cancer. Among those patients with a single, small adenoma — which is considered a low-risk abnormality — the authors reported more than one-half of physicians surveyed would recommend repeat colonoscopy every three years or sooner.

More than 80 percent of the physicians in the study cited clinical evidence in scientific journals as having a major influence in their decisions, and said scientific evidence was significantly more influential than medical guidelines. Information obtained at medical conferences or meetings also was perceived as influential. The authors noted that one problem may be that different medical groups have somewhat differing recommendations, so doctors do not have one single source to turn to for practice guidelines. “Forces in the doctor’s own practice may play a role, as well,” said co-author Martin Brown, Ph.D., of NCI. “This includes concerns about liability, community influence, and financial incentives.”

It may seem that conducting unnecessary colonoscopies in an effort to reduce the rates of colorectal cancer would not be a significant concern. However, overuse of colonoscopy could affect quality of care. Increased wait times as lower-risk individuals get colonoscopies too frequently could result in delayed diagnosis or screening for higher-risk individuals. In addition, colonoscopies can result in complications, such as a reaction to sedation or a tear in the colon wall. For patients considered to have a low risk of colon cancer, the cumulative chance of complications could offset the benefits in cancer reduction. Colonoscopies are also expensive, so unnecessary follow-ups could pose a financial burden to patients and the health care system.

There will be an estimated 57,000 colorectal cancer-related deaths in 2004, making it the second leading cause of cancer mortality after lung cancer. As both the general population and the elderly population continue to increase, the resources for colonoscopy will become more limited, and it is critical that the colonoscopy resources are used efficiently and appropriately.

For more information about cancer, please visit the NCI Web site at http://www.cancer.gov or call NCI's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).

** For more information about USPSTF screening recommendations for colorectal cancer, please visit http://www.ahrq.gov/clinic/3rduspstf/colorectal/colorr.htm.