Abstract 620: Evaluating multiple tumor markers in a novel analysis of reproductive factors and breast cancer risk

Background: Reproductive factors are reported to be differentially associated with risk of breast cancer (BC) subtypes; however, subtype defining markers are highly correlated and clarifying which markers are sources of heterogeneity is challenging. We aimed to define the association of parity, age at first full-term pregnancy (AFFTP), and breastfeeding duration (BFD) with BC subtypes defined by estrogen receptor (ER), progesterone receptor...