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Endometrial profile of tamoxifen and low-dose estradiol combination therapy.

ABSTRACT: Combination estrogen + progestin therapy has been associated with increased breast cancer risk in postmenopausal women. Selective estrogen receptor modulators (SERM) are potential alternatives to progestins, although the endometrial safety of estrogen + SERM co-therapies is not known. The goal of this study was to evaluate the endometrial profile of low-dose estradiol and the SERM tamoxifen alone and in combination.Twenty-four postmenopausal female cynomolgus macaques were randomized by social group to receive placebo, low-dose micronized estradiol (E(2); 0.25 mg/1,800 kcal), the SERM tamoxifen (Tam; 20 mg/1,800 kcal), or E(2) + Tam for 4 months in a parallel-arm design.Tamoxifen alone resulted in overlapping but distinct effects compared with E(2). Both E(2) and Tam increased uterine weight and endometrial thickness, whereas only E(2) increased endometrial proliferation. Morphologic effects were similar for Tam and E(2) + Tam, which both induced stromal fibrosis and cystic change. Tamoxifen inhibited E(2)-induced proliferation and expression of genes related to cell cycle progression while exhibiting mixed agonist and antagonist effects on gene markers of estrogen receptor activity. The gene expression profile for E(2) + Tam was distinct from either E(2) or Tam alone but dominated by the Tam effect for estrogen-regulated genes. Tam also attenuated E(2) effects on both vaginal maturation and cervical epithelial height.These findings characterize a novel phenotype resulting from estrogen + SERM co-therapy. The predominance of Tam effects on endometrial proliferation, morphology, and transcriptional profiles suggests that endometrial risks for E(2) + Tam may be similar to Tam alone.

SUBMITTER: Wood CE

PROVIDER: S-EPMC2818660 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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Endometrial profile of tamoxifen and low-dose estradiol combination therapy.

Wood Charles E CE Kaplan Jay R JR Fontenot M Babette MB Williams J Koudy JK Cline J Mark JM

Clinical cancer research : an official journal of the American Association for Cancer Research 20100126 3

<h4>Purpose</h4>Combination estrogen + progestin therapy has been associated with increased breast cancer risk in postmenopausal women. Selective estrogen receptor modulators (SERM) are potential alternatives to progestins, although the endometrial safety of estrogen + SERM co-therapies is not known. The goal of this study was to evaluate the endometrial profile of low-dose estradiol and the SERM tamoxifen alone and in combination.<h4>Experimental design</h4>Twenty-four postmenopausal female cyn ...[more]

PMID: 20103679

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Project description:ObjectiveThe aim of the study was to evaluate the effect of a single-capsule 17β-estradiol/progesterone (E2/P4), TX-001HR, on endometrial safety, to report on amenorrhea and bleeding patterns of users, and to identify predictors of amenorrhea.MethodsThe REPLENISH trial (NCT01942668) evaluated use of TX-001HR in menopausal women (40-65 y) with vasomotor symptoms (VMS) and a uterus. Women were randomized to daily E2/P4 (mg/mg: 1/100, 0.5/100, 0.5/50, or 0.25/50), or placebo for 12 months. Incidence rate of endometrial hyperplasia was calculated from endometrial biopsies conducted at screening and study completion. Women reported bleeding and spotting in daily diaries. The number of bleeding and/or spotting days and the proportion of women with no bleeding or amenorrhea were compared between treatment and placebo using the Fisher exact test. Predictors of cumulative amenorrhea were assessed by univariate analyses.ResultsWomen (n = 1,835) who took at least one study dose comprised the safety population; 1,255 had baseline and 12-month biopsies and comprised the endometrial safety population. Incidence of endometrial hyperplasia was ≤0.36% with any dose of TX-001HR after 1 year of use (one-sided upper 95% confidence interval ≤4%). Cumulative amenorrhea (no bleeding/spotting) rates increased over time and were relatively high from cycle 1 to 13 with TX-001HR (56%-73%; placebo 79%; P < 0.05 except with 0.25/50 dose). Few vaginal bleeding adverse events (1.0%-4.6% TX-001HR vs 0.7% placebo) were reported and discontinuations due to bleeding were low (0.4%-1.4% vs 0%). Cumulative amenorrhea was significantly more frequent in older women, those further from their last menstrual period, and those with lower baseline E2 concentrations (all; P < 0.01).ConclusionsAll doses of TX-001HR provided endometrial protection and were associated with an improved bleeding profile over time; older age, further last menstrual period, or lower baseline E2 may predict amenorrhea with TX-001HR.

Dataset Information

Endometrial profile of tamoxifen and low-dose estradiol combination therapy.

Publications

Endometrial profile of tamoxifen and low-dose estradiol combination therapy.

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