Hormone therapy for breast cancer involves using medications that interfere with the hormone estrogen, which can promote the growth of certain types of breast cancer. The main types of hormone therapy drugs include: 1. Tamoxifen: This drug blocks estrogen from attaching to cancer cells. It's often used for women who are at high risk of breast cancer or for those who have had early-stage breast cancer. Side effects can include hot flashes and vaginal discharge. 2. Aromatase inhibitors: These drugs prevent the body from making estrogen from other hormones. They are used primarily in postmenopausal women and can help prevent the cancer from spreading. Common side effects include joint pain and bone thinning. 3. Fulvestrant: This injection works by blocking and degrading estrogen receptors on cancer cells. Side effects can include nausea and injection site pain. 4. Elacestrant: This oral drug is a selective estrogen receptor degrader (SERD) that reduces estrogen receptor levels and blocks their activity. Side effects may include fatigue and nausea. These medications are typically recommended for hormone receptor-positive (HR+) breast cancers and are not effective for hormone receptor-negative (HR-) cancers.