Age and Stage Trends in Early-Onset Colorectal Cancer Incidence Before and After the USPSTF 2021 Update.

INTRODUCTION: Early-onset colorectal cancer (CRC) incidence has increased in the US, raising concern about changing risk among adults aged 20-49 years. In 2021, the US Preventive Services Task Force lowered the recommended starting age for average-risk CRC screening from 50 to 45 years. This study examined whether CRC incidence trends were concentrated among adults newly eligible for screening. METHODS: Analyzing the latest SEER data for malignant CRCs from 2004-2023, the study estimated annual percentage changes (APCs) using log-linear regression for adults aged 20-49 years overall and for age groups 20-44, 45-49, and 50-54 years, further stratified by early-stage and late-stage diagnosis. Joint-Point analyses were performed as a sensitivity check. RESULTS: In 2023, there were 10,395 early-onset CRC diagnoses, corresponding to an incidence rate of 18.1 per 100,000. Overall early-onset CRC incidence increased by 1.95% per year in 2004-2019 and 8.41% per year in 2021-2023. The largest recent increase occurred among adults aged 45-49 years, whose all-stage APC rose from 1.31% in 2004-2019 to 14.38% in 2021-2023. Among adults aged 45-49 years, early-stage CRC increased by 32.14% per year in 2021-2023, compared with 0.12% per year in 2004-2019; late-stage CRC increased by 3.29% per year in 2021-2023. Trends among adults aged 20-44 and 50-54 years were comparatively stable, but rising. CONCLUSIONS: Recent acceleration in early-onset CRC incidence was concentrated among adults aged 45-49 years, especially early-stage diagnoses, suggesting increased detection after expanded screening eligibility.