Annual fecal immunochemical testing (FIT) for colorectal cancer screening demonstrated slightly decreased but steady sensitivity and predictive values over several rounds with a high participation rate.
According to the report, noninvasive fecal blood testing has been shown to decrease colorectal cancer (CRC) incidence and mortality. Further, screening with fecal immunochemical testing (FIT) doesn’t require consideration of medications or dietary factors as guaiac stool testing does.
Dr. Christopher Jensen of the Kaiser Permanente Division of Research in Oakland, Calif., and colleagues conducted a retrospective cohort study of 50- to 70-year-olds to assess the performance of FIT for 4 years of annual screening. Their results were published in Annals of Internal Medicine.
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In total, 670,841 participants received FIT kits and 48.2% returned completed kits. Among the participants in round 1, 55.4% were white, 46.4% were men, and the mean age was 58.5 years. In subsequent rounds, eligible participants returned the kits at a rate of 75.3% for round 2, 83.4% for round 3, 86.1% for round 4, and 63.8% overall.
Tests were 5% positive in the first round and ranged from 3.7% to 4.3% positive in subsequent rounds. Further, men compared with women (5.1% versus 3.7%) and older participants compared to younger (5.2% versus 4.1%) had higher rates of FIT positivity. Follow-up colonoscopy was obtained within 1 year (median 45 days) of a positive FIT in 78.4% of participants.
The positive predictive value for adenoma was highest in the first round at 51.5% and ranged from 47.4% to 48.5% in subsequent rounds. Similarly, the positive predictive value for colorectal cancer was 3.4% in the first round and ranged from 2.1% to 2.3% in subsequent rounds.
Finally, the sensitivity of FIT for CRC was 84.5% in the first round and between 73.4% and 78% in subsequent rounds. Across all screening rounds, participants with a diagnosis with CRC had a positive FIT between 79.7% in round 1 to 75.3% in round 4 beforehand. The authors point out that sensitivity was slightly lower for proximal compared with distal cancer. Further, those with a positive FIT the year prior were less likely to have advanced-stage CRC (26.9%) than those with a negative FIT (33.1%) or not screened (37.1%).
Dr. Corley and Dr. Levin reported grants from the National Cancer Institute, which supported the study. Dr. Jensen reported grants from the National Institutes of Health, and Dr. Doubeni reported consulting for Exact Sciences.