Tamoxifen and Endometrial Neoplasia: Updated Statements from the American College of Obstetricians and Gynecologists

The selective estrogen receptor modulator (SERM) tamoxifen is often prescribed as adjuvant therapy for breast cancer in women who are not candidates for aromatase inhibitors. This agent is also approved for prevention of breast cancer in high-risk women and treatment of metastatic breast cancer. Tamoxifen's efficacy results from its antiestrogenic properties in breast tissue; however, as an estrogen agonist in reproductive tissues, this SERM raises risk for endometrial proliferation, hyperplasia, polyps, adenocarcinoma (in postmenopausal women), and uterine sarcoma, and may also contribute to the growth of endometriosis, adenomyosis, and leiomyoma. Prior guidelines recommended that adjuvant tamoxifen therapy be continued for ≤5 years; howev…