Fecal Immunochemical Test to Detect Colorectal Neoplasia in Lynch Syndrome: A Prospective Multicenter Study

Colonoscopy surveillance for Lynch syndrome is burdensome and postcolonoscopy colorectal cancers (CRCs) still occur. The noninvasive fecal immunochemical test (FIT) might guide optimal colonoscopy intervals.

Prospective, multicenter observational study in which individuals with Lynch syndrome performed a quantitative FIT before high-quality surveillance colonoscopy. Diagnostic performance of FIT at various thresholds ≤20 μg Hb/g feces was assessed for relevant neoplasia, including advanced neoplasia (CRC, advanced adenomas [AAs] and advanced serrated lesions [ASLs]) and non-advanced adenomas (NAAs).

Of the 217 included individuals (59% female, median age 51 years), 4 had CRC, 5 AA, 4 ASL, and 57 NAA as most relevant neoplasia. The lowest FIT positivity threshold (2.5 μg Hb/g feces, 14% positivity rate) maximized detection: 4/4 CRCs, 4/5 AA, 1/4 ASL, and 9/57 NAA were detected, resulting in a sensitivity and negative predictive value of, respectively, 89% and 99% for CRC plus AA, 69% and 97% for advanced neoplasia, and 26% and 72% for all relevant neoplasia (91% specificity for all groups). At equal sensitivity and negative predictive value, specificity for advanced neoplasia optimized to 94% at threshold 4.1 μg/g. Per 100 FITs at threshold 4.1 μg/g, 11 individuals would test positive and thus proceed to colonoscopy, 2 individuals with advanced neoplasia would be missed and 3 individuals would need colonoscopy to detect 1 advanced neoplasia.

FIT at thresholds ≤4.1 μg Hb/g feces may be a promising strategy to postpone colonoscopy in approximately 9 of 10 individuals with Lynch syndrome. Large validation studies that also provide gene variant-specific outcomes should be prioritized.