Age‐Specific Trends in Carcinoma Incidence Among Adolescents and Young Adults in the United States, 1975–2021

INTRODUCTION: The incidence of carcinomas among adolescents and young adults (AYAs; ages 15-39) is rising. However, most research treats AYAs as a single group, potentially obscuring important age- and sex-specific trends. This study examined long-term trends in carcinoma incidence among AYAs in the U.S., overall and by 5 year age groups. METHODS: We conducted a population-based, retrospective time-series analysis using data from eight U.S. cancer registries in the Surveillance, Epidemiology and End Results database. The study included 128,255 AYAs diagnosed with malignant carcinoma between 1975-2021. Average annual percent change (AAPC) in incidence rates was estimated using Joinpoint regression, stratified by age, sex, and carcinoma subtype. RESULTS: A total of 128,255 individuals, aged 15-39, who were diagnosed with carcinoma between 1975-2021; 77.5% of AYA carcinoma cases occurred in females. The overall incidence of carcinomas increased by 0.61% (CI: 0.43-0.80) per year in AYAs from 1975 to 2021, with similar increases observed in females (AAPC: 0.68%; 95% CI, 0.50-0.87) and males (AAPC: 0.71%; 95% CI, 0.45-0.97). When stratified by age group, overall carcinoma incidence increased in each 5-year group; the largest relative increase was in those aged 15-19 (AAPC: 1.66%; 95% CI, 0.71-2.62) and the smallest was in those aged 35-39 (AAPC: 0.48%; 95% CI, 0.22-0.74). CONCLUSIONS: Carcinoma incidence is increasing in the AYA population within each 5-year age group, including among adolescents, a group in which these cancers have historically been rare. These findings highlight the urgent need to investigate the causes of this increase to guide targeted prevention and early detection efforts.