Endometrial changes in postmenopausal breast cancer patients receiving tamoxifen

To assess the estrogenic effect of tamoxifen and associated pathologic changes of the endometrium in postmenopausal breast cancer patients.

The endometrium of 103 gynecologically asymptomatic postmenopausal breast cancer patients was examined. Fifty-one had been treated with tamoxifen and 52 had not received any hormonal treatment. The two groups were similar in age, parity, age at menopause, and body mass index.

Compared with the control subjects, the tamoxifen patients had a thicker endometrium (mean +/- standard deviation 10.4 +/- 5.0 versus 4.2 +/- 2.7 mm; P = .0001) and larger uterine volume (45 +/- 27 versus 25 +/- 11 cm3; P = .001), as determined by transvaginal sonography. Hysteroscopy showed an atrophic endometrium in 28% of the patients in the tamoxifen group, as compared with 87% of the control patients (P = .0001). Endometrial polyps were more frequent in the tamoxifen group (36 versus 10%; P = .004), which included one patient with atypical hyperplasia, one with adenomatous hyperplasia, and one with endometrial adenocarcinoma; two controls had endometrial adenocarcinoma.

The results provide evidence for an estrogenic effect of long-term tamoxifen treatment on the postmenopausal uterus and show it to be associated with an increased occurrence of polyps.