Risk for women is 1 in 8 throughout life.
Obesity is a decreased risk for breast cancer premenopausally.
Postmenopausally, this risk factor increases significantly. Breast feeding for six months reduces a woman's risk for breast cancer. Regular exercise, bilateral premenopausal oopherectomies all reduce breast cancer risk. Tamoxifen - evaluated in the breast cancer prevention trial. There was an increase in endometrial cancers, though, and there was a significant negative quality of life score.