Hormonal prevention of hereditary breast cancer.

Women who carry a mutation in the BRCA1 or BRCA2 genes face a lifetime risk of developing breast cancer that approaches 80%. Among women with predisposing BRCA mutations, the risk of breast cancer is influenced by environmental factors and by modifying genes. Through the study of cohorts of female BRCA1 and BRCA2 carriers, several modifying factors have been identified. The risk of breast cancer is increased by early parity and is decreased by breast feeding, by oophorectomy, and by cigarette smoking. Many of the stragegies for breast cancer prevention involve estrogen deprivation and it is important to consider the acute and long-term effects of induced menopause in young women at high risk for breast cancer. There are no data so far on whether hormonal replacement therapy is hazardous in carriers of BRCA mutations.