National Breast Cancer Coalition

Truth #19: Hormone replacement therapy (HRT) increases your risk of breast cancer

TRUE. According to the Women's Health Initiative (WHI) Postmenopausal Hormone Therapy Trials—an estrogen-plus-progestin replacement therapy—increases the risk of breast cancer, along with heart disease, stroke and blood clots.

The WHI clinical trials, launched in 1991, studied a group of 161,808 generally healthy postmenopausal women for the effects of HRT, diet modification and calcium and vitamin D supplement use on heart disease, fractures as well as breast and colorectal cancer. Results from the trial on HRT, published in 2002, found that while the estrogen-only replacement therapy did not increase breast cancer risk, the risks far outweighed the benefits in the estrogen-plus-progestin study. Overall, there was a 24% increase in the risk for breast cancer due to estrogen-plus-progestin.