Bilateral oophorectomy (BO) has been shown to decrease breast cancer risk.127,128 Surgical or chemical deprivation of ovarian hormones has been associated with a decrease in breast cancer risk, recurrence, and death.129–133 Also, risk-reducing oophorectomy in BRCA1/2 carriers leads to a significant reduction (by 40%-50%) of breast cancer risk and death in most studies.134 These findings suggest a causal role of endogenous ovarian hormones in breast cancer risk. The gene discussed is BRCA1; the disease is breast cancer.