There are different recommendations for the use of drugs to reduce the risk of breast cancer depending on whether a woman has been through menopause. Menopause is the time in woman's life when the ovaries stop producing eggs and her menstrual periods have stopped for 12 months in a row. For a woman who has had a hysterectomy (surgical removal of the uterus), blood tests are used to determine if she has been through menopause. A woman who has been through menopause is postmenopausal, and a woman who is still having menstrual periods is premenopausal or perimenopausal. Perimenopause is the time (about three to five years) before menopause when a woman's menstrual periods become irregular.

Based on whether a woman has been through menopause, ASCO recommends the following.

• Women who have an increased risk of breast cancer may take tamoxifen for five years to reduce their risk of ER-positive invasive cancer. The risk may still be reduced for another five years after stopping tamoxifen. It is not known if there is a benefit to taking tamoxifen for more than five years. Both premenopausal and postmenopausal women may take tamoxifen.
• Women who have gone through menopause and have an increased risk of breast cancer may take raloxifene for five years to reduce the risk of ER-positive invasive breast cancer. Postmenopausal women with osteoporosis may take raloxifene for longer than five years.
• ASCO does not recommend the use of aromatase inhibitors to reduce the risk of breast cancer.
• ASCO does not recommend the use of retinoids, such as fenretinide, to lower breast cancer risk.