Incidence of early-onset colorectal cancer in the United States: A population-based analysis (2000-2019).

e15676 Background: The incidence of colorectal cancer (CRC) among individuals younger than 50 years has been increasing in the United States, while rates among older adults have declined. Understanding demographic patterns of early-onset CRC is essential to inform prevention and screening strategies. We examined temporal trends in early onset CRC incidence overall and stratified by sex and race using population-based cancer registry data. Methods: We conducted a descriptive epidemiologic study using data from the Surveillance, Epidemiology, and End Results (SEER) 17 registries. Incident cases of malignant colorectal cancer diagnosed between 2000 and 2019 were identified. Early-onset CRC was defined as diagnosis before age 50 years; late-onset CRC was defined as diagnosis at age 50 years or older. Age-adjusted incidence rates per 100,000 person-years were calculated using SEER*Stat and standardized to the 2000 US standard population. Incidence rates were summarized across predefined calendar periods (2000–2004, 2005–2009, 2010–2014, and 2015–2019) and stratified by sex and race. Temporal changes were assessed descriptively using absolute and relative differences in incidence rates. Results: Between 2000 and 2019, 93,186 early-onset and 746,447 late-onset CRC cases were identified. Among individuals younger than 50 years, age-adjusted CRC incidence increased steadily from 6.0 per 100,000 in 2000–2004 to 8.4 per 100,000 in 2015–2019, representing an approximate 40% increase. In contrast, incidence among individuals aged 50 years and older declined from 173.1 to 116.1 per 100,000 over the same period. Early-onset CRC incidence was consistently higher among males than females, increasing from 6.4 to 8.7 per 100,000 in males and from 5.6 to 8.0 per 100,000 in females between 2000–2004 and 2015–2019. Racial disparities were observed, with Black individuals experiencing the highest incidence across all periods (7.6 to 8.6 per 100,000), while White individuals demonstrated a substantial increase over time (5.8 to 8.6 per 100,000). Asian or Pacific Islander populations had lower incidence overall but showed steady increases. Estimates among American Indian/Alaska Native individuals were based on small case counts and were less stable. Conclusions: Early-onset colorectal cancer incidence increased substantially in the United States from 2000 to 2019, in contrast to declining incidence among older adults. Rising rates were observed across sexes and racial groups, with persistently higher incidence among males and Black individuals and notable increases among White individuals. These findings highlight a growing public health burden of early-onset CRC and underscore the need for targeted prevention strategies and continued evaluation of age-based screening recommendations.