Endometrial changes with tamoxifen: comparison between tamoxifen-treated and nontreated asymptomatic, postmenopausal breast cancer patients.

Endometrial thickness, as evaluated by vaginal ultrasonography, and endometrial histologic findings, as well as demographic characteristics, health habits, and risk factors for endometrial cancer, were compared between 93 asymptomatic postmenopausal breast cancer patients who had been on tamoxifen treatment and 20 patients who had not. The mean ultrasonographic endometrial thickness in the women on tamoxifen treatment was 13.1 +/- 10.4 mm, which was significantly thicker than the 4.0 +/- 3.2 mm found in the nontreated women (P = 0.001). The frequency of endometrial pathological findings was remarkably high (35.5%) among the tamoxifen-treated patients, compared with nontreated patients (20.0%), with a P value of 0.058 and an odd ratio of 4.6. Thus, it is suggested that the remarkably high prevalence of pathological endometrial changes was due to the continuous and unopposed exposure of the endometrium to tamoxifen.