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Clin Cancer Res. 2007 Jul 15;13(14):4185-90.

Effect of tibolone on breast cancer cell proliferation in postmenopausal ER+ patients: results from STEM trial.

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1
Division of Special Gynecology, Medical University of Vienna, Vienna, Austria.

Abstract

PURPOSE:

Tibolone is a selective tissue estrogenic activity regulator, approved for the treatment of vasomotor symptoms in postmenopausal women. We have done an exploratory, double-blind, randomized, placebo-controlled pilot trial to investigate the tissue-specific effects of 2.5 mg tibolone on breast cancer in postmenopausal women, in particular on tissue proliferation (STEM, Study of Tibolone Effects on Mamma carcinoma tissue).

EXPERIMENTAL DESIGN:

Postmenopausal women with initially stage I/II, estrogen receptor-positive (ER+) primary breast cancer, were randomly assigned to 14 days of placebo or 2.5 mg/d tibolone. Core biopsies of the primary tumor were obtained before and after treatment. Ki-67 and apoptosis index were analyzed in baseline and corresponding posttreatment specimen.

RESULTS:

Of 102 enrolled patients, 95 had evaluable data. Baseline characteristics were comparable between both treatment groups. Breast cancer cases are mainly invasive (99%), stage I or II (42% and 50% respectively), and ER+ (99%). Median intratumoral Ki-67 expression at baseline was 13.0% in the tibolone group and 17.8% in the placebo group, and decreased to 12.0% after 14 days of tibolone while increasing to 19.0% in the placebo group. This change from baseline was not significantly different between tibolone and placebo (Wilcoxon test; P=0.17). A significant difference was observed between the treatment groups when the median change from baseline apoptosis index was compared between the treatment groups (tibolone, 0.0%; placebo, +0.3%; Wilcoxon test; P=0.031). The incidence of adverse effects was comparable.

CONCLUSIONS:

In ER+ breast tumors, 2.5 mg/d tibolone given for 14 days has no significant effect on tumor cell proliferation.

PMID:
17634547
DOI:
10.1158/1078-0432.CCR-06-2700
[Indexed for MEDLINE]
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