Incidence and Long-Term Outcomes of Interval Colorectal Cancers in a Fecal Immunochemical Test Screening Program

Background: Survival of colorectal cancer detected within a screening program may largely affect the effectiveness of the screening program. Long-term outcomes of interval cancers after a fecal immunochemical test (FIT) and colonoscopy (interval type post-colonoscopy colorectal cancer; PCCRCi) within a FIT screening program are, however, rarely reported. Methods: The interval cancers occurring within a Taiwan Colorectal Cancer Screening Program in 2004-2012 comprised the study cohort and were followed until 2016. The incidence of FIT interval cancers and PCCRCi was calculated, and PCCRCi were stratified by adenoma detection rate (ADR) levels [ 42% (high)]. The survival status of those with FIT interval cancers and different PCCRCi categories were compared. Findings: In total, 2,746,478 subjects received at least one FIT screening with 1,825 (86·4%) FIT interval cancers and 288 (13·6%) PCCRCis developing during the study period. Hospitals with low ADR levels had a significantly higher incidence of PCCRCi (0·93 per 1000 person-years) than those with middle and high ADR levels (0·70 and 0·58 per 1000 person-years, respectively) (p<0·001). PCCRCi in the high ADR group presented at a more advanced stage (48·0% at stage III/IV) and had the worst survival compared with PCCRCi in other ADR groups and FIT interval cancers (p=0·004). In multivariable analysis, when compared with PCCRCi in the middle ADR group, the adjusted hazard ratio of colorectal cancer death was 1·07 (95% Confidence Interval [CI]=0·60–2·26) for PCCRCi in the low ADR group, 1·64 (95%CI=1·19–2·26) for FIT interval cancer, and 1·94 (95%CI=1·01–3·80) for PCCRCi in the high ADR group.  Interpretation: Screening programs should elaborate on reducing interval cancers via different approaches, considering their magnitude and long-term outcomes, to secure its effectiveness. Different etiological and biological bases may play a key role in PCCRCi of different ADR levels. Funding Information: This study was supported by the Health Promotion Administration, Ministry of Health and Welfare, Taiwan. Declaration of Interests: None. Ethics Approval Statement: This study was approved by the Health Promotion Administration, Ministry of Health and Welfare of the Taiwanese government.