NEWS

Recent Studies Unite Groups in ‘Convergence of Thought’ on Colorectal Cancer Screening

Tom Reynolds

Colorectal cancer is one of the few cancers for which screening has been shown in randomized clinical trials to reduce mortality from and incidence of the disease. But it could save many more lives and prevent far more cancers if more people used one of the many tests available, and advocates say the time is ripe for a concerted effort to boost screening rates.

Agencies and organizations producing colorectal cancer screening guidelines have reached a consensus where confusion once reigned, insurers are increasing coverage for the procedures, and people are beginning to talk more openly about the disease and its prevention, said Bernard Levin, M.D., head of the Division of Cancer Prevention at the University of Texas M. D. Anderson Cancer Center, Houston, and chair of the National Colorectal Cancer Roundtable.

"Until recently, the topic has eluded public—and to some extent, professional—attention," Levin said. Compared with other cancers, "There isn’t as much realization that colorectal cancer is highly curable when detected early and is preventable by removing the precancerous polyps detected by screening." Only 44% of Americans older than age 50—the recommended age to start screening for colorectal cancer—had a recent screening test, according to data published by the Centers for Disease Control and Prevention in 2001.

"I think it reflects cultural bias against anything to do with the colon and rectum," Levin added. "But clearly, we have now made some progress; for example, Katie Couric has helped to make colonoscopy a subject of public discussion." The NBC Today Show co-anchor’s husband died of colon cancer, and in March 2000, millions of TV viewers watched as Couric’s colonoscopy was televised in an effort to increase awareness about colorectal cancer screening.

Four methods are currently used for screening: fecal occult blood test (FOBT), colonoscopy, flexible sigmoidoscopy, and double contrast barium enema (DCBE). In the past, various groups recommended different screening tests and schedules, and federal and private insurers varied widely in their coverage.

"Now, a lot of this has been overcome," Levin said. "There has been a convergence of thought on the importance of screening and on the best approaches to yield a cost-effective result."

During the 1990s, one randomized trial in Minnesota and three in Europe showed FOBT to be an effective screening tool. A 1998 meta-analysis of these trials found that annual, home-based FOBT reduced mortality from colorectal cancer by 16% and incidence of the disease by about 20%. Preliminary positive results on flexible sigmoidoscopy in a trial in the United Kingdom were reported in 2002, and case–control study data support these findings. Evidence for the effectiveness of colonoscopy is less direct, coming mostly from its use in follow-up diagnosis in FOBT trials.

In July 2002, the U.S. Preventive Services Task Force upgraded its recommendation for colorectal cancer screening to Level A, meaning it "strongly recommends that clinicians routinely provide the service to eligible patients" based on good evidence that screening improves important health outcomes and that benefits substantially outweigh harms. However, the task force did not recommend a specific screening test, citing insufficient evidence to show which strategy is best.

Medicare now covers colorectal cancer screening, including colonoscopy. Private insurance coverage is variable, Levin said, but many insurers will at least cover FOBT and flexible sigmoidoscopy.

In the February 2003 issue of Gastroenterology, the U.S. Multisociety Task Force on Colorectal Cancer published updated guidelines for screening based on findings that have come to light since the group’s original guidelines were published in 1997. The task force represents the American College of Gastroenterology, American College of Physicians/American Society of Internal Medicine, American Gastroenterological Association, and American Society for Gastroenterology. The American Cancer Society has also endorsed the task force guidelines.

For individuals at average risk without a family history or other known risk factors for colorectal cancer, changes from the 1997 guidelines include no rehydration for FOBT (it produces too many false positives), use of colonoscopy in preference to barium enema for diagnostic evaluations after a positive FOBT, and a shortened interval for DCBE screening from 10 years to 5 years. Other changes address genetic testing and screening for people with familial colorectal syndromes, and surveillance of patients who have had polyps or tumors removed. The task force acknowledges that emerging methods—such as virtual colonoscopy and DNA testing of stool—show "substantial promise," but are not ready for clinical use outside of a study setting.

Meanwhile, the National Committee for Quality Assurance (NCQA), a nonprofit group that measures the quality of care offered by U.S. health plans, is proposing to add colorectal cancer screening to its Health Plan Employer Data and Information Set (HEDIS), a set of standardized performance measures designed to help insurance purchasers and consumers compare managed care plans.

Eric Schneider, M.D., assistant professor of medicine at Harvard Medical School and Harvard School of Public Health in Boston, was a member of the team that developed the proposed measure. He said that only in the past few years has a consensus emerged to make a HEDIS measure of colorectal cancer screening feasible.

"The major issue was a lack of consensus about the time intervals for testing and uncertainty about the evidence for colonoscopy as an alternative [to FOBT]," said Schneider. "A concern raised early on was whether one of these strategies would emerge as the preferred strategy or the only strategy. And what’s happened instead is that the guidelines have essentially come to agreement that all of the strategies are acceptable." HEDIS has become the de facto standard for comparing and monitoring health plans, he said, so that before adding a measure to this data set, NCQA must have confidence that the measured intervention will remain standard practice in the foreseeable future.

The proposed new measure for colorectal cancer screening, which was open for public comment until March 21, would assess the proportion of health plan members who receive FOBT during the measurement year, flexible sigmoidoscopy or DCBE within the past 5 years, or colonoscopy during the past 10 years. It will begin with private reporting to NCQA in 2004 and public reporting in 2005.

"We expect that once this measure gets out there, it will catch people’s attention and that a lot more effort will be dedicated to increasing the screening rate," Schneider said.

He noted that there are tradeoffs among the screening methods: colonoscopy is invasive and costly, yet can be effective when performed just once every 10 years. FOBT is cheap and noninvasive, but must be repeated annually and relies on the patient to comply with stool sampling for 3 days and possibly to discontinue some medications. "And if there’s a positive FOBT ... they’re going to end up getting a colonoscopy anyway," he added. Sigmoidoscopy and DCBE are in between FOBT and colonoscopy on the convenience-versus-invasiveness continuum.

Some questions remain. As the U.S. Preventive Services Task Force noted, "It is unclear whether the increased accuracy of colonoscopy compared with alternative screening methods (for example, identification of lesions that FOBT and flexible sigmoidoscopy would not detect) offsets the procedure’s additional complications, inconvenience, and costs."

In the August 7, 2002, issue of the Journal of the National Cancer Institute, William Anderson, M.D., of the National Cancer Institute’s Division of Cancer Prevention; Levin; and co-authors suggested that a randomized trial comparing colonoscopy with other screening tests, with colorectal cancer mortality as the endpoint, would be ideal scientifically but is unlikely to be feasible. Such a trial would need to enroll roughly 100,000 subjects and cost tens of millions of dollars, they estimated. Instead, they suggested that smaller trials be mounted to evaluate emerging technologies against surrogate endpoints such as adenoma.

In October 2002, the Cancer Research Foundation of America (http://www.preventcancer.org, now known as the Cancer Research and Prevention Foundation) published a report on strategies to increase CRC screening rates. The foundation calls for a national, federally funded colorectal screening program modeled after the National Breast and Cervical Cancer Early Detection Program.

The report cites estimates that incidence of colorectal cancer could be reduced by 60%, and mortality by 80%, if compliance with initial screening rose to 60% and follow-up testing to 80%, and that widespread screening could save 20,000 lives per year.

"The message that screening can prevent colorectal cancer must be emphasized," the foundation noted. "People generally think that screening for cancer means determining that you already have the disease."

While optimistic, the authors caution that "sweeping changes in health care practices do not happen overnight. ... It took a concerted breast cancer awareness campaign several years before screening mammography began to increase. The American health care system heeded the public’s demand for improvements in that service. It is time to do the same for colorectal cancer screening."



             
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