Uterine side effects of treatment with tamoxifen

Abstract

Objective: To assess a causal the relationship between endometrial lesions and tamoxifen therapy in patients with breast cancer. Design: Prospective longitudinal study and cross-sectional study. Setting: Cancer prevention unit at Basurto Hospital, Bilbao. Population and methods: Three populations of breast cancer were studied: 43 before the beginning of tamoxifen; 78 after 5–72 months of tamoxifen, and 34 before tamoxifen and after 12–24 months of tamoxifen treatment (PAIRED GROUP). All of them were systematically studied with CO 2 diagnostic hysteroscopy and endometrial biopsy by the same clinician. Results: Before tamoxifen, the following endometrial lesions were detected: endometrial polyps 9.3%; endometrial cysts 16.3%; synechiae 11.6%. In the paired group the ingestion of tamoxifen shows a direct causal effect with a significant increase in endometrial polyps (11.8% vs. 29.4%; OR=13; CI=7.9–18.1), in endometrial cysts (17.7% vs. 55.9%; OR=7.5; CI=5.9–9.1) and in synechiae (14.7% vs. 35.5%; OR=8; CI=4.7–11.3). In the group under tamoxifen for 5–72 months, one endometrial carcinoma was detected. Conclusions: Breast cancer patients have a number of endometrial lesions before undergoing any hormonal therapy. Tamoxifen significantly increased benign endometrial lesions, usually after less than one year of treatment. No cases of endometrial carcinoma was found in our series of 34 patients with 1–2 years of tamoxifen treatment, and 1/78 in patients with 5–72 months of tamoxifen.