Population-based breast cancer incidence by age, sex, subtype, and stage.

Abstract

e22620 Background: Granular estimates of breast cancer incidence by age, sex, molecular subtype, and stage are essential for understanding disease burden and informing prevention, screening, treatment, and research priorities. Registry-based data provide clinical detail but reflect a subset of the U.S. population, while nationally representative estimates often lack comparable granularity. Methods: We analyzed data from eligible Surveillance, Epidemiology, and End Results (SEER) cancer registries and the Global Burden of Disease (GBD) 2023 study to estimate age- and sex-specific breast cancer incidence by molecular subtype and stage in the United States. SEER data were used to derive subtype and stage distributions within by year, age, and sex. Stage categories included localized, regional, and distant disease, consistent with SEER Summary Stage definitions.Year-specific SEER subtype and stage-within subtype distributions were used directly. For strata with missing estimates, distributions were imputed using a stepwise approach, prioritizing estimates from a recent reference year (2017) and, if unavailable, pooled estimates across years within the same age and sex group. Distributions were then temporally smoothed using LOWESS on the logit scale with renormalization. After harmonization by location, year, age, sex, and cancer type, GBD incidence estimates were proportionally redistributed using the smoothed SEER-derived subtype and stage-within-subtype distributions to generate nationally representative incidence estimates. Results: This approach enabled nationally representative quantification of absolute breast cancer burden by molecular subtype, stage, and finer age groupings not available from registry data alone. In 2022, a substantial portion of the national burden occurred among women aged 50–69 years. Within this age range, HR+/HER2- disease accounted for the greatest number of incident cases, with an estimated 29,309 cases (95% UI: 25,189–33,731) among women aged 65–69 years (incidence rate: 298 per 100,000). HR-/HER2- disease also contributed substantial burden in this age group (3,611 cases; 95% UI: 3,103–4,156; incidence rate: 37 per 100,000). In contrast, HER2+ subtypes peaked at younger ages within the 50–69 range. Across molecular subtypes, localized-stage disease accounted for the largest proportion of incident cases. Conclusions: Integrating registry-derived subtype and stage distributions with nationally representative incidence estimates enables more granular characterization of breast cancer burden than registry data alone. These population-based estimates may inform national cancer surveillance and research prioritization by aligning incidence burden with clinically relevant subtype and stage stratifications.