Tamoxifen Several methods of additive hormone treatment can be used for patients in relapse. Tamoxifen is the treatment of choice for the first recurrence in premenopausal and postmenopausal women. Tamoxifen is thought to act by depleting estrogen receptors in breast cancer cells, but it may have another mechanism of cytotoxicity. In postmenopausal women, an objective response as high as 50 to 60 percent that lasts from nine to 16 months can be expected in those patients with the favorable characteristics mentioned. Fewer than 10 percent of patients with unfavorable characteristics will respond.
Tamoxifen is associated with little toxicity.
An increase in endometrial cancer has also been observed in breast cancer patients who are given tamoxifen. Endometrial cancer develops in approximately 1.6 per 1,000 women who are treated with tamoxifen, compared with 0.2 per 1,000 women who are not treated with tamoxifen. In patients who experience vaginal bleeding while taking tamoxifen, measurement of endometrial thickness by ultrasonography and endometrial biopsy are indicated. It would be imprudent not to recommend tamoxifen as an adjuvant therapy for mastectomy or lumpectomy and irradiation for primary breast cancer when indicated, because the benefits of tamoxifen are substantially greater than the risk of endometrial cancer. There has been concern that tamoxifen may accelerate osteoporosis.