Can Colorectal Screening Incorporate Adherence into Guidelines?

The U.S. Preventive Services Task Force’s (USPSTF’s) draft recommendations for colorectal cancer (CRC) screening acknowledge there are several viable screening options that can accurately detect early-stage CRC, including annual fecal immunochemical test (FIT) or high-sensitivity, guaiac-based fecal occult blood test (gFOBT); annual FIT plus flexible sigmoidoscopy every 10 years; or colonoscopy every 10 years. Yet, the USPSTF acknowledges that test characteristics are determined from studies of one-time use, rather than repeated screening over time, as would be seen in real-world application of the recommendations. This raises concerns about screening accuracy in real-world settings, where adherence rates are low.

“The important practical issue is whether an annual FOBT should continue to be recommended in current U.S. guidelines without further qualification, when it has been known for decades that adherence to a program of annual FOBT testing is low, resulting in poor effectiveness of the overall screening strategy,” writes co-author Sidney Winawer, M.D., from Memorial Sloan Kettering Cancer Center in New York, in a viewpoint published May 17 in the Journal of the American Medical Association.

The USPSTF draft statement, released in October 2015, updates previous recommendations published in 2008. Over that time period, an additional 95 new studies were published and considered, including 24 studies assessing the impact of screening on CRC incidence and mortality, 19 new studies evaluating the diagnostic accuracy of screening tests, and 70 new studies that evaluated harms. Yet, no comparative studies (head-to-head studies between screening methods) were conducted that demonstrated one recommended screening strategy to be more effective than others.

Data shows though, that colonoscopy remains the most commonly used CRC screening test in the United States (more than 60 percent), while stool tests account for about 10 percent. It is widely known that CRC screening adherence is suboptimal, although improving. Recent U.S. estimates show that the overall proportion of adults “up to date” on CRC screening increased from 54 percent in 2002 to 65 percent in 2010, but nearly one-third of adults remain “never screened.” Retesting adherence rates are higher in clinical trials and organized health plans (i.e., Veterans Administration [VA]), but even still, rates of annual retesting over four years remain as low as 14 percent, according to a VA study.

“In order for colorectal cancer screening programs to be successful in reducing deaths from the disease, they need to involve more than just the screening method in isolation. Screening is a package or cascade of activities that must occur in concert, cohesively, and in an organized way for benefits to be realized,” writes the USPSTF in its draft recommendation.

The recommendations do address effective implementation strategies that have been demonstrated to increase appropriate use of CRC screening, including the use of clinician and client reminder systems, the use of small media (videos, letters, and brochures), reducing structural barriers to screening (time or distance to the screening delivery setting), and providing clinician assessment and feedback about screening rates.”

“The question therefore becomes how best to recommend FOBT in CRC screening guidelines. Should FIT be offered with a more careful consideration of its retesting adherence?” writes Winawer and colleagues. “The FIT retesting adherence effectiveness relationship should be carefully considered in future CRC screening guidelines to maximize the effectiveness of a frequently used test. ... This would provide evidence-based guidelines with a critical pragmatic and reality-driven component.”

Takeaway: While several CRC screening strategies appear effective based on one-time trials, future guidelines may need to address the effect that lack of adherence to testing strategies has on effectiveness.