Stage gap and projected metastatic surge for young-onset colorectal cancer: A decade-long call to action.

e15702 Background: By 2023,1 in 10 colon cancers and 1 in 4 rectal cancers will occur under age 50. Young-onset colorectal cancer (YOCRC) often presents at advanced stages (stage III and IV) and is the leading cause of cancer death under age 50. To inform strategies for mitigating disease burden in the decade ahead, we aimed to estimate the projected 5-year (by 2027) and 10-year (by 2032) trends in stage distribution of YOCRC. Methods: Data from patients diagnosed with histologically confirmed colon or rectal cancer from 2004 through 2022 were queried from the Surveillance, Epidemiology, and End Results (SEER) 21 cancer registry. The age-adjusted incidence rate (per 100,000 population) was calculated and stratified by age at diagnosis (young onset [YO]: 18-49 years, vs. later-onset [LO]: 50+ years), stage (local, regional, distant) and location (colon versus rectosigmoid and rectum). Annual percentage changes (APCs) and p-values of trends were determined using SEER*Stat software. The predicted incidence rates were calculated using estimated APCs assumed to change at a constant percentage of the previous year’s rate. Projected percent change was reported relative to 2022 incidence rates. Results: Among 816,417 patients, 99,951 (12.2%) had YO and 716,466 (87.8%), LO disease. Relative to 2022, the incidence of metastatic disease among YO patients is projected to increase by 13.5% in 5 years (2027) and 28.8% in 10 years (2032). Similarly, regionally advanced disease is projected rise by 10.9% and 23.0% at 5- and 10 years, respectively. Localized disease is projected to remain stable overall. In contrast, among LO patients, incidence is projected to decline across all stages by 2027 (localized −19.5%, regional −11.1%, distant −7.1%) and further by 2032 (localized −35.2%, regional −21.0%, distant −13.8%). Most alarmingly, site-specific analyses for YO patients projected to 2032 highlight pronounced increases in metastatic (+47.7%) and in regionally advanced (+44.5%) rectal cancer cases, followed by that of metastatic (+23.3%) and regional-advanced (+14.6%) colon cancers. Localized disease is expected to remain largely stable for colon cancer, with a slight decline for rectal cancer (−2.1% by 2027; −4.2% by 2032). Projected over the same decade, for LO adults, the largest declines are expected in incidences of localized colon (-20% by 2027; - 36.0% by 2032) and localized rectal (-17.7% by 2027; -32.3% by 2032) cancers. Conclusions: A significant age-based divergence in the trajectory of regionally advanced and metastatic CRC incidence is projected over the next decade. Within the next decade, 1 in 5 advanced-stage diagnoses of CRC will occur in young adults under age 50, with the largest increases seen in metastatic and locally advanced rectal cancers. These data highlight the urgency for implementing screening and treatment interventions.