Patterns in Cancer Incidence Among People Younger Than 50 Years in the US, 2010 to 2019

IMPORTANCE Emerging data suggest that the incidence of early-onset cancers, defined as cancers diagnosed in people younger than 50 years, is increasing, but updated data are limited. OBJECTIVE To characterize the patterns in the incidence of early-onset cancers in the US from 2010 to 2019 and provide granular data on the cancers with the fastest-growing incidence rates. DESIGN, SETTING, AND PARTICIPANTS This population-based cohort study analyzed data from 17 National Cancer Institute Surveillance, Epidemiology, and End Results registries from January 1, 2010, to December 31, 2019. Age-standardized incidence rates per 100 000 people were extracted for early-onset cancers, with rates age adjusted to the US standard population. A total of 562 145 patients with early-onset cancer between 2010 and 2019 were identified and included. Data were analyzed from October 16, 2022, to May 23, 2023. MAIN OUTCOMES AND MEASURES Primary outcomes were incidence rates and descriptive epidemiological data for people younger than 50 years with cancer. The annual percentage change (APC) of the age-standardized incidence rate was estimated using the Joinpoint regression program. RESULTS Among 562 145 patients (324 138 [57.7%] aged 40-49 years; 351 120 [62.5%] female) with early-onset cancer, 4565 (0.8%) were American Indian or Alaska Native, 54 876 (9.8%) were Asian or Pacific Islander, 61 048 (10.9%) were Black, 118 099 (21.0%) were Hispanic, 314 610 (56.0%) were White, and 8947 (1.6%) were of unknown race and/or ethnicity. From 2010 to 2019, the age-standardized incidence rate of early-onset cancers increased overall (APC, 0.28%; 95% CI, 0.09%-0.47%; P =.01) and in female individuals (APC, 0.67%; 95% CI, 0.39%-0.94%; P =.001) but decreased in male individuals (APC, -0.37%; 95% CI, -0.51% to -0.22%; P <.001). In contrast, the age-standardized incidence rate of cancers in individuals aged 50 years and older decreased over the study period (APC, -0.87%; 95% CI, -1.06% to -0.67%; P <.001). In 2019, the highest number of incident cases of early-onset cancer were in the breast (n = 12 649). From 2010 to 2019, gastrointestinal cancers had the fastest-growing incidence rates among all early-onset cancer groups (APC, 2.16%; 95% CI, 1.66%-2.67%; P <.001). Among gastrointestinal cancers, those with the fastest-growing incidence rates were in the appendix (APC, 15.61%; 95% CI, 9.21%-22.38%; P <.001), intrahepatic bile duct (APC, 8.12%; 95% CI, 4.94%-11.39%; P <.001), and pancreas (APC, 2.53%; 95% CI, 1.69%-3.38%; P <.001). CONCLUSIONS AND RELEVANCE In this cohort study, the incidence rates of early-onset cancer increased from 2010 to 2019. Although breast cancer had the highest number of incident cases, gastrointestinal cancers had the fastest-growing incidence rates among all early-onset cancers. These data may be useful for the development of surveillance strategies and funding priorities.