ABSTRACT
BACKGROUND: Colorectal cancer screening (CRCS) needs to be pandemic-resilient to avoid long-lasting shutdowns; however, realistic participation target remains unelucidated. This study aimed to identify the lowest acceptable participation rate in CRCS during a pandemic, focusing on vulnerable older populations who require urgent intervention. METHODS: This nationwide cross-sectional study included 80,946 inpatients aged 70-85 years who were first diagnosed with colorectal cancer (CRC) after 70 years of age, between April 1, 2014 and March 31, 2019, in Japan. To evaluate the association between area-level CRCS participation rate and individual early CRC detection, a multilevel logistic regression model was constructed. The mandatorily implemented screening rates were converted to the total screening rate equivalents (TSREs), which reflect the remaining contributions of voluntarily provided screenings. RESULTS: Early detections during stages 0-I were significantly observed when primary screening rate was ≥38% (TSRE) and combined follow-up rate was ≥85%. For early detection during Tis-T1, primary screening rate ≥ 38% (TSRE) and combined follow-up rate ≥ 90% were necessary. For follow-up rates ≥70% or ≥75%, there were cases where missed detection of Tis-T1 were observed. CONCLUSION: The results indicate that, even during pandemic, CRCS should achieve a primary screening rate of 38% and follow-up rate of 85% for vulnerable older populations. These values, lower than the current desirable rates, suggest the maximum possible compromise in balancing the resources between cancer screening and pandemic measures. Moreover, they also indicate the minimum target for shifting to fecal immunochemical test-focused program. Further explorations with varied CRCS settings are necessary for verification.