Spotlight on fecal immunochemical testing

Three recent studies looked at the effects of fecal immunochemical test (FIT) screening after negative colonoscopy, delays in time from positive FIT to colonoscopy, and a large colorectal screening program that used FIT with opportunistic colonoscopy.

The first study suggested that the time from positive FIT to colonoscopy should not exceed nine months. In a systematic review, researchers looked at the association between time to colonoscopy after positive FIT and colorectal cancer incidence. Eight studies were included, with five reporting outcomes based on time from positive FIT to colonoscopy (the remaining three were reported based on time from positive fecal occult blood test [FOBT] to colonoscopy). Results were published online on Sept. 30 by Clinical Gastroenterology and Hepatology.

Compared to colonoscopy performed within one month of positive fecal-based colorectal cancer screening, colonoscopy performed beyond nine months was significantly associated with a higher incidence of colorectal cancer, with adjusted odds ratios of 1.75 and 1.48 in the two largest observational studies. Longer time delay to colonoscopy was also associated with more advanced cancer stage at diagnosis and higher colorectal cancer-specific mortality. The study was primarily limited by the observational design of the included studies and the fact that attrition rates were relatively high, the authors noted.

“An understanding of these findings is crucial for primary care physicians, endoscopists, administrators of endoscopy units and [colorectal cancer] program planners. … [W]e propose that wherever possible, colonoscopy should not be delayed beyond 6 months of positive fecal testing as an aspirational target (with 9 months as an upper limit),” they concluded.

The second study found that FIT screening after negative colonoscopy may reduce the risk of incident colorectal cancer. Through 2014, researchers followed individuals with a negative colonoscopy after positive FIT in the first screening in the Taiwanese Colorectal Cancer Screening Program from 2004 to 2009. They compared the incidence of colorectal cancer between those who did and did not receive subsequent FIT screening. Results were published online on Sept. 28 by Gut.

The study included 9,179 participants, 6,195 of whom received subsequent FIT during the study period. The colorectal cancer incidence per 1,000 person-years was 1.34 in patients who received subsequent FIT and 2.69 in those who did not (adjusted hazard ratio, 0.47; 95% CI, 0.31 to 0.71). The risk of incident colorectal cancer increased with higher baseline fecal hemoglobin concentration. Limitations of the study include the possibility of residual confounding and self-selection bias, as well as the fact that it used hospital-level rather than endoscopist-level adenoma detection rate data, the authors noted. “Further exploration is mandatory to further elucidate the appropriate timing and frequency of subsequent FIT and to identify the population such an approach may benefit, based on the level of [fecal hemoglobin concentration],” they concluded.

The third study reported the outreach strategies that led to more than 80% participation during one year of a large colorectal cancer screening program in an integrated U.S. health system that used FIT with opportunistic colonoscopy. Researchers retrospectively analyzed a cohort of adult patients ages 51 to 75 years during 2017 in the Kaiser Permanente Northern California health system. Results were published online on Sept. 30 by Clinical Gastroenterology and Hepatology.

Among 1,023,415 screening-eligible individuals, 405,963 (40%) were up to date with screening at baseline. The health system mailed a FIT kit to 507,401 of the 617,452 who were not up to date. Of the entire cohort, 206,481 (20%) completed FIT within 28 days of mailing, another 61,644 (6%) did so after an automated call at week 4, and 40,438 others (4%) did so after a mailed reminder letter at week 6. During the program year, more than 800,000 medical record screening alerts were generated and about 295,000 FIT kits were distributed during patient office visits. About 100,000 FIT kits were ordered during direct-to-patient calls by medical assistants, and 111,377 patients (11%) completed FIT outside of the automated outreach period. Another 13,560 patients (1%) completed a colonoscopy, sigmoidoscopy, or FOBT unrelated to FIT. Cumulatively, 839,463 (82%) of eligible patients were up to date with screening at the end of the year, and 12,091 of 14,450 patients (84%) with positive FIT had diagnostic colonoscopy. The primary study limitation was the lack of a comparison group or time point to evaluate the various screening program components, the authors noted.