Shifts in the Proportion of Distant Stage Early-Onset Colorectal Adenocarcinoma in the United States

Background: Carcinoids, frequently classified as "colorectal cancer"contribute to rising early-onset colorectal cancer (EOCRC) incidence rates (IR) and have distinct staging distributions compared to often advanced stage adenocarcinomas (screening target). Thus, assessing temporal shifts in early-onset distant stage adenocarcinoma can impact public health. Methods: 2000-2016 Surveillance Epidemiology and End Results (SEER) 18 yearly adenocarcinoma IRs were stratified by stage (in situ, localized, regional, distant), age (20-29, 30-39, 40-49, 50-54-yearolds), subsite (colorectal, rectal-only, colon-only), and race [non- Hispanic whites, non-Hispanic Blacks (NHB), Hispanics] in 103,975 patients. Three-year average annual IR changes (pooled 2000-2002 IRs compared with 2014-2016) and cancer stage proportions (percent contribution of each cancer stage) were calculated. Results: Comparing 2000-2002 with 2014-2016, the steepest percent increases are in distant stage cancers. Colon-only, distant adenocarcinoma increased most in 30-39-year-olds (49%, 0.75/ 100,000!1.12/100,00, P < 0.05). Rectal-only, distant stage increases were steepest in 20-29-year-olds (133%, 0.06/100,000!0.14/ 100,000, P < 0.05), followed by 30-39-year-olds (97%, 0.39/ 100,000!0.77/100,000, P < 0.05) and 40-49-year-olds (48%, 1.38/100,000!2.04/100,000, P < 0.05). Distant stage proportions (2000-2002 to 2014-2016) increased for colon-only and rectal-only subsites in young patients with the largest increases for rectal-only in 20-29-year-olds (18%!31%) and 30-39-year-olds (20%!29%). By race, distant stage proportion increases were largest for rectalonly in 20-29-year-old NHBs (0%!46%) and Hispanics (28%!41%). Distant colon proportion increased most in 20-29- year-old NHBs (20%!34%). Conclusions: Youngest patients show greatest burdens of distant colorectal adenocarcinoma. Although affecting all races, burdens are higher in NHB and Hispanic subgroups, although case counts remain relatively low.