Early-onset colorectal cancer in Sweden: increase in distal tumors but a shift in right-sided incidence, 2020-2024.

Early-onset colorectal cancer (EOCRC; age <50 years) has increased in high-income countries. We updated a nationwide Swedish cohort study with data from 2020-2024 to compare recent trends with those reported during 1993-2019. Using the National Cancer Register, we identified all incident EOCRC at ages 20-49 years. Temporal trends in age-standardized incidence were assessed using segmented Poisson regression with a breakpoint at 2020 to estimate annual percentage changes (APCs). A total of 1,616 EOCRC cases were diagnosed during 2020-2024. APCs for left-sided colon and rectal cancers were consistent with continued increases in incidence. In contrast, right-sided colon cancer showed a significant change in trend (P = 0.01), with a non-significant decline during 2020-2024 (APC -3.48, 95% CI - 7.88-1.14). These findings indicate that the continued rise in EOCRC is primarily driven by distal tumors, i.e., left-sided colon and rectal cancers. Continued surveillance is needed to clarify long-term patterns and underlying drivers.