Endometrial Effects of Tamoxifen and Exemestane in Early Breast Cancer: Final Results of a Randomized Phase III Trial

ABSTRACT Background Tamoxifen (T) has been for a long time the treatment of choice in hormonal receptor positive early breast cancer patients (EBCP). It is known that T has partial estrogen agonistic activity on uterus determining an increase in gynecological symptoms. Long-term T treatment can lead to an increased incidence of endometrial cancer. The availability of aromatase inhibitors (AI) has modified the prescription options in postmenopausal breast cancer patients while remaining the standard of care in premenopausal setting. AI do not mediate their effects through the estrogen receptor potentially conferring tolerability advantages to women particularly in relation to their effects on the endometrium. So far some studies including all the available AI have been published which confirmed the lack of estrogen effects of AI on endometrium compared to T. In 2001 we started a phase III study comparing T and Exemestane (E) in EBCP in order to evaluate the differences in the endometrial changes recorded by transvaginal ultrasound (TVUS). Material and methods Postmenopausal hormonal receptor positive EBCP were randomly assigned to receive T or E. A baseline TVUS was performed and repeated after 6 and 12 months. The primary end-point, endometrial thickness (ET) was evaluated with T-test. Results From 2001 to 2008 220 patients were enrolled in our department. Patients' characteristics were well balanced in each arm. Definitive results are summarized in the table: ET (median) Baseline ET (median) After 6 m p (ET baseline vs 6 months) ET (median) After 12 m p (ET baseline vs 12 months) E 3 (1.4-5) 3 (1.17-9.3) NS 2.8 (0.02-13.5) NS T 3 (0.14-5) 6.64 (1.9-19.7) 6 (1.93-25.2) Conclusions Our results confirmed the data obtained in similar studies. In particular E was associated with significantly less endometrial thickening than T during the projected period of therapy in postmenopausal hormone receptor positive EBCP. Disclosure All authors have declared no conflicts of interest.