Clinicopathologic Characteristics, Treatments, and Survival Outcomes of Early-onset Compared to Later-onset Colorectal Mucinous Adenocarcinomas: A Population-based SEER Analysis.

BACKGROUND: Colorectal mucinous adenocarcinoma (CMA) is a unique subtype of adenocarcinoma. This study aimed to compare characteristics, treatments, and survival outcomes of early-onset and later-onset CMA. METHODS: This investigation was a retrospective cohort study from the National Cancer Institute's SEER Research Data database from 2000 to 2022 on patients with CMA. Patients aged < 50 years (early-onset) and patients aged ≥ 50 years (later-onset) were compared regarding disease characteristics, treatments, and survival. The main outcome measures were 5-year overall survival (OS) and cancer-specific survival (CSS). RESULTS: The study included 55,853 patients; 10.4% of them presented with early-onset disease. Early-onset CMA more often affected males, Blacks, and Hispanics, and was more advanced and more often associated with liver metastases. Early-onset CMA was associated with higher 5-year OS (57.7% vs. 47.5%, p < 0.001) and CSS (58.4% vs. 45.4%, p < 0.001). In multivariable Cox proportional hazard analysis excluding postdiagnosis treatment variables, later-onset CMA was associated with higher all-cause mortality (HR: 1.69, 95% CI 1.53-1.87, p < 0.001) and cancer-specific mortality (HR: 1.45, 95% CI 1.30-1.61, p < 0.001) compared to early-onset disease. In a sensitivity analysis adjusting for treatment variables, these associations persisted, although they were attenuated for both OS (HR: 1.56, 95% CI 1.41-1.72, p < 0.001) and CSS (HR: 1.34, 95% CI 1.20-1.49, p < 0.001). CONCLUSIONS: Early-onset CMA presented with different demographic and disease characteristics and treatment patterns than later-onset disease. Survival of early-onset CMA was higher than later-onset CMA.