Does tamoxifen use affect prognosis in breast cancer patients who develop endometrial cancer?

The use of tamoxifen to prevent breast cancer and decrease recurrence is not controversial. However, the effect that tamoxifen may have in women with a history of breast cancer in whom endometrial cancer develops is unclear. The purpose of this study was to estimate whether a history of tamoxifen use is a prognostic factor for such patients. Between 1990 and 2002, patients seen at The University of Texas M. D. Anderson Cancer Center with a history of breast cancer who developed endometrial cancer were identified. Medical records were reviewed to identify clinical, pathologic, and outcome information. Eighty-nine patients with a history of breast cancer in whom endometrial carcinoma developed were identified. Fifty-two percent (46/89) had a history of tamoxifen use (median duration 48 months; range 2-120 months). There were no significant differences in the clinical or pathologic features between tamoxifen users and nonusers. A history of tamoxifen use was associated with a shorter interval from breast cancer to endometrial cancer diagnosis (77.2 versus 121.3 months for nonusers; P =.01). There was no significant difference in overall survival between tamoxifen users and nonusers (39.2 months versus 48.3 months, P =.27), and there was no difference in endometrial cancer-specific survival duration between tamoxifen users and nonusers (55.7 versus 51.0 months, P =.92). Among tamoxifen users, the interval from breast cancer to endometrial cancer diagnosis was significantly shorter than that in nonusers. In this cohort, a history of tamoxifen use was not associated with a worse overall or disease-specific survival.