Uterine cancer in patients treated with tamoxifen for breast cancer

Objective: To evaluate the incidence of uterine cancer in women with breast cancer who had been treated with Tamoxifen. Material and methods: We evaluate 463 women who were treated with 20mg of Tamoxifen daily for a hormone dependent breast cancer, and followed up for 6 years. Results: We detected 7 uterine cancers (1.55% of the study population and 2.52 % women a year). Of these, 5 were endometrial carcinomas, a malignant heterologous mixed mesodermal tumour and one endometrial stromal sarcoma. Only the rapid growth of what we believed to be a uterine myoma, detected by ultrasound, allowed us to diagnose the endometrial stromal sarcoma. The other 6 tumours were detected by the appearance of vaginal bleeding, in spite of the annual controls carried out on the study group. Conclusions: We find a higher incidence of uterine cancer in women with Tamoxifen treated breast cancer, but it is not the double of the general population. We found mainly endometrial carcinomas, although there were also 2 sarcomas (an endometrial stromal sarcoma and a malignant heterologous mixed mesodermal tumour).