Trends in Early-Onset Colorectal Adenocarcinoma and Neuroendocrine Tumors Across Racial and Ethnic Groups.

Early-onset colorectal cancer (EOCRC), defined as diagnosis before age 50, is increasing despite declining colorectal cancer (CRC) rates among older adults. Emerging evidence suggests widening racial and ethnic disparities. We aimed to characterize long-term EOCRC incidence and mortality trends across racial and ethnic groups in the United States with comparisons by tumor subtype. We conducted a population-based analysis using United States Cancer Statistics data (2001-2021) for EOCRC incidence and National Center for Health Statistics data (2000-2022) for mortality. Analyses were stratified by race/ethnicity and histology. Trends were quantified using average annual percent change (AAPC) with 95% confidence intervals (Cis). Among 474,601 early-onset adenocarcinoma (EO-ADC) cases, incidence increased in all racial and ethnic groups except Non-Hispanic Black individuals, in whom incidence declined (AAPC = -0.35%, 95% CI -0.63 to -0.08; = 0.01). The steepest incidence increases occurred among American Indian/Alaska Native (AIAN; AAPC = 3.39%, 95% CI 2.70-4.15), Hispanic (AAPC = 0.94%, 95% CI 0.61-1.30), and Asian/Pacific Islander populations (AAPC = 0.64%, 95% CI 0.37-0.95; all < 0.001). EOCRC mortality increased among AIAN (AAPC = 2.67%, 95% CI 1.26-4.26; = 0.001) and Hispanic populations (AAPC = 0.81%, 95% CI 0.39-1.27; < 0.001), but declined among Black individuals (AAPC = -1.08%, 95% CI -1.29 to -0.77; < 0.001). Neuroendocrine tumors increased more rapidly than adenocarcinomas across all groups. EOCRC incidence and mortality are rising most rapidly among AIAN and Hispanic populations. Distinct incidence trajectories of colorectal neuroendocrine tumors compared with adenocarcinomas highlight the importance of histology-specific analyses for accurate epidemiologic interpretation.