Effect of colorectal cancer screening on long‐term survival of colorectal cancer patients: Results of the Korea National Cancer Screening Program

The Korea National Cancer Screening Program (KNCSP) provides fecal immunochemical test-based colorectal cancer (CRC) screening for people aged ≥50 years. Our study aimed to investigate the long-term survival effects of CRC screening based on screening history and interval time since screening. The study cohort was obtained by linking three national databases, namely the Korea Central Cancer Registry, KNCSP database and Death Certificate. We included 32 509 CRC patients diagnosed in 2008 to 2009, who underwent CRC screening via the KNCSP between 2004 and 2009. The patients were followed-up until 2019, and their survival was assessed according to their CRC screening history. Cox proportional hazards regression was used to compare time to deaths among CRC patients according to CRC screening history, after adjusting for covariates. Of the 32 509 patients, 20 022 (61.5%) patients were alive by the end of 2019. Long-term survival was significantly higher among screened patients (68.2%) than nonscreened (57.2%) individuals. Compared to never-screened patients, the hazard ratio (HR) for CRC-specific death in screened patients was 0.77 (95% CI%, 0.73-0.80). Lowest HR was observed in screened, localized CRC patients (HR, 0.48; 95% CI, 0.42-0.56); HR for CRC-specific death was the lowest in patients screened within 12 months of diagnosis (HR, 0.70; 95% CI, 0.66-0.74), following which, the HRs increased with increasing time interval. CRC screening was positively associated with favorable prognosis in CRC patients aged 50 to 79 years. The effects on long-term survival according to interval time was the best among individuals screened within 1 year before diagnosis.