Pregnancy and its association with breast cancer tumor subtypes

Abstract

Parity is associated with a short–term increase in breast cancer (BC) risk followed by a long–term decrease in risk. BC diagnosed 5–7 years after a completed pregnancy is associated with worse outcomes. BC is not a single disease. The dual effect of pregnancy could account for the BC characteristics at presentation (i.e. younger age and more advanced disease) and worse outcomes observed among Hispanics, relative to Non–Hispanic Whites. The purpose of this study was to investigate the association of reproductive characteristics by tumor subtype in a case series of women of Mexican–descent. Cases diagnosed ≤10 years following a birth had nearly 3 times the odds of a diagnosis with HER2+ tumors, relative to ER+/PR+ tumors. HER2+ tumors are associated with reduced survival compared to ER+/PR+ tumors. Diagnosis within a recent pregnancy may contribute to the aggressiveness of BC observed among women of Mexican descent ≤50 years of age.