Annual screening with the fecal immunochemical test is highly sensitive for detecting colorectal cancer and “is feasible and effective for population-level colorectal cancer screening,” according to a large-scale retrospective cohort study assessing this test over four rounds of annual screening. “Overall, programmatic fecal immunochemical test screening detected 80.4% of patients with colorectal cancer diagnosed within 1 year of testing, including 84.5% in round one and 73.4% to 78.0% in subsequent rounds,” Christopher D. Jensen, PhD, MPH, of Kaiser Permanente, Division of Research, and colleagues reported in the Annals of Internal Medicine.
Study participants were Kaiser Permanente Northern and Southern California health plan members who were aged 50 to 70 years at the time of the first fecal immunochemical test mailing date in 2007 or 2008, completed the first round of fecal immunochemical test, and were followed for up to four screening rounds. The mean age of round one participants was 58.5 years; 46.4% were men; and 55.4% were white. The investigators noted that this health-plan membership “is diverse and similar in socioeconomic characteristics to the region’s census demographics.”
Previous studies have shown that the fecal occult blood test reduces colorectal cancer incidence and mortality, and annual fecal occult blood test has been recommended by the U.S. Preventive Services Task Force and the U.S. Multi-Society Task Force on Colorectal Cancer as an option for colorectal cancer screening for average-risk patients between the ages of 50 and 75 years. Both fecal occult blood test and fecal immunochemical test are noninvasive and can be delivered by mail, but fecal immunochemical test does not require any dietary or medication restrictions. Fecal immunochemical test “also has higher detection rates for colorectal cancer and advanced adenomas than guaiac-based stool tests,” the study authors noted.
Of the 670,841 patients invited for screening, 323,349 patients (48.2%) participated in round one. Among those remaining eligible, participation was 75.3%, 83.4%, and 86.1%, respectively, in rounds two, three, and four. (Patients became ineligible for screening if they subsequently had sigmoidoscopy or colonoscopy as well as if they dropped out of the health plan or died. Those who became ineligible because they had sigmoidoscopy or colonoscopy continued to be followed for colorectal cancer.)
Test results were positive (≥ 20 μg of hemoglobin/g) for 5.0% of patients in the first round, with lower estimates of 3.7% to 4.3% in subsequent rounds. “Effective colorectal cancer screening requires follow-up colonoscopy after a positive result,” the authors asserted. In this study, 78.4% received colonoscopy within 1 year of a positive result. In addition, 2.1% had sigmoidoscopy, 5.4% had gastroenterology consultation, and 10.7% had a primary care visit, for a total of 96.6% of participants having some follow-up within 12 months of obtaining a positive result.
Predictive value estimates for colorectal cancer (defined as the “percentage of participants with a positive fecal immunochemical test result who had colorectal cancer diagnosed within 1 year after the result date”) were highest in the first round (3.4%) and lower but stable in subsequent rounds (2.1% to 2.3%). Adenoma predictive value estimates (“among participants with a positive fecal immunochemical test result receiving follow-up colonoscopy within 1 year after the result, the percentage of those in whom an adenoma or advanced adenoma [that is, with villous or tubulovillous histology] were diagnosed”) were available only for the northern California health-plan members but were also highest in round one (51.5%) and lower but stable in subsequent rounds (47.4% to 48.5%). ■
The primary funding source for the study was the National Institutes of Health.
Jensen CD, et al: Ann Intern Med. January 26, 2016 (early release online).