Endometrial profile of low-dose estradiol and tamoxifen combination therapy

Combination therapy with estrogen and a selective estrogen receptor modulator (SERM) is a promising approach to safely alleviate important side effects related to estrogen deficiency in women at high risk for breast cancer. Data related to endometrial safety of estrogen+SERM co-therapies are limited, however. The primary goal of this study was to evaluate the endometrial profile of low-dose E2 and Tam alone and in combination. In this study 16 postmenopausal female cynomolgus macaques were randomized to receive placebo, low-dose micronized estradiol (E2, 0.25 mg/1800 kcal), the SERM tamoxifen (Tam, 20 mg/1800 kcal), or E2+Tam in a parallel-arm design. Endometrial samples were collected after 4 months of treatment and used for microarray analysis.