Incidence Rate Trends of Breast Cancer Overall and by Molecular Subtype by Race and Ethnicity and Age.

Importance: Black and Hispanic women in the US experience higher incidence rates of aggressive molecular subtypes of breast cancer, including triple-negative disease. However, how these rates are changing, particularly across different age groups, has not been well documented. Objective: To assess changes in overall and subtype-specific breast cancer incidence rates in the US by age and race and ethnicity. Design, Setting, and Participants: This cohort study used Surveillance, Epidemiology, and End Results program cancer registry data from 22 US cancer registries on 1 123 658 females who received a diagnosis of invasive breast cancer from 2010 to 2019. Statistical analysis was conducted from August 2023 to October 2024. Exposures: Age and race and ethnicity. Main Outcomes and Measures: Age-adjusted incidence rates of invasive breast cancer overall and across the 4 major molecular subtypes by age and by race and ethnicity, as well as their associated annual percentage changes using Joinpoint Trend Analysis software. Results: Of the 1 123 658 participants in the study, 219 112 (19.5%) were younger than 50 years, 409 257 (36.4%) were aged 50 to 64 years, and 495 289 (44.1%) were 65 years or older. A total of 141 703 participants (12.6%) were Hispanic, 3253 (0.3%) were non-Hispanic American Indian or Alaska Native, 78 306 (7.0%) were non-Hispanic Asian or Pacific Islander, 124 560 (11.1%) were non-Hispanic Black, 769 043 (68.4%) were non-Hispanic White, and 6793 participants (0.6%) had an unknown race and/or ethnicity. Overall, breast cancer incidence rates increased 0.5% per year from 2010 to 2019. Variation by race and ethnicity was observed, with increases of 1.4% per year among Hispanic females, 1.9% per year among non-Hispanic American Indian or Alaska Native females, and 2.1% per year among non-Hispanic Asian or Pacific Islander females, while rates increased only 0.8% per year among non-Hispanic Black females and 0.5% per year among non-Hispanic White females. In subtype analyses, increases of the greatest magnitude in recent years were observed in the incidence rates of triple-negative breast cancer per year among participants aged 65 years or older (Hispanic females, 2.3%; non-Hispanic Asian or Pacific Islander females, 5.5%; and non-Hispanic Black females, 4.3%), while remaining unchanged among non-Hispanic White females. Conclusions and Relevance: In this cohort study of 1 123 658 females with breast cancer over the 10-year period from 2010 to 2019, there were substantial differences in trends in the incidence rates of breast cancer overall and by subtype across different racial and ethnic groups. Further research is needed to understand the factors associated with these trends.