Variation in breast cancer subtypes with age and race/ethnicity

Background: Both age and race have been identified as independent predictors of breast cancer subtype but the association of age with subtype within each race is not well understood. This study assesses the association of age with the eight breast cancer subtypes as defined by ER/PR/HER2 among white, African-American, Hispanic, and Asian/Pacific Islander women. Methods: This study included 69,358 women with primary invasive breast cancer. Logistic regression was used to assess the association of age with each of the ER/PR/HER2 subtypes for each race adjusted for socioeconomic status, stage, grade, and tumor size. Results: The odds of African-American women having a triple-negative tumor were not statistically significantly increased for women under 46 when compared to the African-American women aged 46-69 (OR = 0.96; 95% CI = 0.80-1.16). A similar pattern was observed for the ER-/PR-/HER2+ subtype. Hispanic women under age 46 (OR = 0.83; 95% CI = 0.71-0.97) and over age 70 (OR = 0.71; 95% CI =0.57-0.89) were less likely to have the ER-/PR-/HER2+ subtype. Asian/Pacific Islander women under age 46 also had reduced odds (OR = 0.67; 95% CI = 0.55-0.82) of the ER-/PR-/HER2+ subtype. Conclusions: The ER/PR/HER2 subtypes vary with age and differences in this variation depend on race. It is important to define breast cancer using the ER/PR/HER2 subtype and the significance of age and race should not be overlooked. (C) 2009 Elsevier Ireland Ltd. All rights reserved.