Rectal and sigmoid colon cancers drove the rise in early-onset colorectal cancer incidence, increasing annually by 4.15% and 3.86%, respectively, in individuals under 50.
The recent rise in early-onset colorectal cancer incidence in the US is primarily driven by increases in rectal and sigmoid colon cancers across all demographic groups.
Abstract Background: Early-onset colorectal cancers (EOCRCs) diagnosed in people younger than 50 are increasing in incidence in the U.S., though the causes are unclear. We studied recent trends in EOCRC incidence and survival in the U.S. Methods: De-identified data from the National Cancer Institute Surveillance, Epidemiology, and End Results Program (SEER 21) was used to evaluate colorectal cancer (CRC) cases diagnosed in the U.S. in 2013-2022 (excluding 2020) by demographic and clinic-pathologic characteristics including age, sex, race, tumor site, stage, histology, and county-level measures of rurality, annual household income, poverty, and education using SEER*Stat. Average annual percent change was calculated using Joinpoint. Age-standardized 5-year relative and disease-specific survival rates were calculated using time from cancer diagnosis to death or last contact. Results: Overall CRC incidence declined from 2013-2022 in a manner that was more pronounced for colon and rectosigmoid junction cancers than rectal cancers. Among individuals aged 50+, incidence significantly declined for all subsites except for the rectum. Among individuals younger than 50, colon and rectal cancers significantly increased 2.50% and 4.15% annually, respectively. Rectal cancers showed the highest annual increase among EOCRCs, followed by sigmoid colon (3.86%, p = 0.002), splenic flexure (2.97%, p = 0.048), overlapping lesion/not otherwise specified (NOS) colon (1.79%, p = 0.01), transverse colon (1.38%, p 0.001), and ascending colon (1.08%, p 0.001). Increases in EOCRCs were observed for all sex, race/ethnicity, stage, and county-level rurality, income, poverty, and education groups, with significantly higher annual increases for metropolitan compared with nonmetropolitan counties (3.05% vs. 1.78%, p 0.001). Adenocarcinomas (NOS) and neuroendocrine tumors (NET) accounted for increases in both early-onset colon (3.05% and 1.50%) and rectal cancers (4.15% and 7.42%). Survival was lower for individuals aged 50+; males compared with females; Blacks compared with Whites; regional and distant stages compared with localized; single individuals compared with married; and nonmetropolitan, lower income and education, and higher poverty counties. Survival was significantly lower for mucinous adenocarcinomas and higher for NET and hematologic cancers compared with adenocarcinomas (NOS). Conclusions: The recent increase in EOCRC incidence has been driven by increases in rectal and sigmoid colon cancer incidence, which showed the steepest growths and equally across all demographic and socioeconomic groups, and were diagnosed at younger ages and at more advanced stages compared with other anatomical subsites. These findings highlight the need to elucidate biological and environmental mechanisms underlying the rise in EOCRC to inform prevention and intervention efforts. Citation Format: Michelle O. Nagata, Scott K. Kuwada, Linda Wong, Loïc Le Marchand, Brenda Y. Hernandez. Rectal and sigmoid colon cancers drive rising early-onset colorectal cancer incidence in the United States abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2336.
Nagata et al. (2026) studied this question. Rectal and sigmoid colon cancers drove the rise in early-onset colorectal cancer incidence, increasing annually by 4.15% and 3.86%, respectively, in individuals under 50.