Fecal Immunochemical Test in Colorectal Cancer Screening: Colonoscopy Findings by Different Cut-off Levels

Background And Aim: Fecal immunochemical test (FIT) is used in colorectal cancer (CRC) screening, but number of tests and cut-off level differ by program. The aim was to evaluate CRC screening with two FIT samples in average-risk 60-year-old men and women and to investigate hemoglobin (Hb) level in correlation to adenoma characteristics.

Methods: We analyzed a cohort from Screening of Swedish Colons trial where participants with at least one of two FIT samples ≥10 μg Hb/g are offered colonoscopy. FIT levels and colonoscopy findings were assessed in multivariable analyses. Cut-off levels 10-80 μg Hb/g for one and two samples were assessed. FIT levels and advanced neoplasia (AN) were investigated by gender.

Results: A total of 12 383 participated and 1182 positives (551 women) completed colonoscopy diagnosing 27 (2.3%) CRC and 269 (23%) advanced adenomas (AA). Median FIT level was 241.0 and 23.8 for CRC and AA compared with 13.4-15.8 in other subgroups (P = 0.002) correlating with adenoma size (P = 0.038). CRC was detected in 22 and 19 subjects for the first sample at cut-off 20 and 40 μg Hb/g, compared with 20 and 17 for the mean of two samples at cut-off 40 and 80 μg Hb/g (P < 0.05). Men had more AN (CRC + AA), (P = 0.003). In women, similar number of AN would be detected with cut-off lowered from 40 to 20 or from 80 to 40 μg Hb/g, requiring additional 26-34% colonoscopies.

Conclusion: In average-risk 60-year-olds, FIT was higher in participants with AN and correlated with adenoma size. FIT screening with one sample at low cut-off detected more CRC than two samples at higher cut-off. Applying lower cut-off in women to equalize gender differences in AN would result in considerable increase in colonoscopy workload.