Reproductive and hormonal factors, family history, and breast cancer according to the hormonal receptor status

The aim of this study was to investigate the association between breast cancer risk, reproductive factors, and family history of breast cancer by the estrogen receptor (ER) and progesterone receptor (PR) status. We analyzed data from an Italian case-control study including 1075 women with incident breast cancer and 1477 hospital controls. We estimated the odds ratios (ORs) of breast cancer using unconditional logistic regression models including major recognized risk factors for breast cancer. Stronger associations with ER+ than with ER- breast cancer were observed for parity (OR: 0.7 vs. 0.9 for ≥ 3 births vs. nulliparae), age at first birth (OR: 1.6 vs. 1.2 for age ≥ 30 vs. <25 years), menopausal status (OR: 0.7 vs. 0.8 for postmenopause vs. pre/perimenopause), age at menopause (OR: 1.3 vs. 1.2 for menopause at age ≥ 50 vs. <50 years), and family history of breast cancer (OR: 2.2 vs. 1.4). Among the ER+ patients, the presence of PR+ did not appreciably modify any of the risk estimates. The association with age at menarche and hormone replacement therapy use was neither significant nor heterogeneous across ER and PR subtypes. In conclusion, we found stronger associations with selected menstrual and reproductive factors for ER+ (PR+) than for ER- (PR-) breast cancers, though in the absence of significant heterogeneity.