The effect of tamoxifen on the endometrium.

Tamoxifen (Nolvadex), a nonsteroidal antiestrogen, was first approved by the FDA for the treatment of patients with breast cancer in 1978. Large clinical trials have demonstrated a recurrence-free and overall survival benefit in both pre- and postmenopausal women. Long-term adjuvant tamoxifen is the endocrine treatment of choice for selected patients with breast cancer, and large-scale trials are currently underway to evaluate its role as a chemopreventive agent in healthy women at risk for breast cancer. Consequently, a large number of women will be subjected to both the benefits and potential risks of long-term tamoxifen therapy. One of the most significant potential complications is the development of endometrial cancer. The estimated annual risk of endometrial cancer in tamoxifen-treated patients is approximately 2 per 1,000 women. Most of these cancers will be detected at an early stage when they are highly curable. The potential benefit of tamoxifen treatment in breast cancer patients outweighs this risk; however, all patients receiving tamoxifen should undergo regular gynecologic evaluations.