Postmenopausal hormone therapy before and after breast cancer: clinical experiences

Effects of tibolone and conventional HRT on the expression of estrogen and progesterone receptors in the breast

OBJECTIVE

There is evidence that long-term hormone replacement therapy (HRT) is associated with an increased breast cancer risk. The aim of this study was to assess the effects of tibolone on estrogen and progesterone receptors in comparison to the effects of conventional HRT in the breast of surgically postmenopausal macaques.

METHOD

Sixty macaques were bilaterally ovariectomized 3 months before hormonal treatment was initiated. The animals were randomized into four treatment groups, including tibolone (TIB), conjugated equine estrogens (CEE), conjugated equine estrogens+medroxyprogesterone acetate (CEE+MPA) and control animals (C). After 2 years treatment, breast tissues were collected, fixed and paraffin embedded. Immunohistochemistry assays with monoclonal antibodies for estrogen receptors (ERalpha and ERbeta) and progesterone receptors (PRA and PRB) were performed.

RESULTS

The expression of ERalpha was markedly decreased in the CEE+MPA group as compared to C and TIB groups. The TIB group was not different from the C and CEE groups. No significant differences were found for ERbeta immunostaining. The expression of PRA was strongly increased in the TIB group as compared to the C and CEE+MPA groups. Immunostaining of PRB was increased in the CEE and TIB treated animals as compared to both C and CEE+MPA groups.

CONCLUSIONS

Tibolone increased the expression of both PRA and PRB, without affecting ERalpha and ERbeta expression in the macaque breast. These findings indicate that the effects of tibolone in breast tissue could be mediated via differential regulation of PRA and PRB isoforms and therefore distinct from those observed with conventional HRT.

Effect of Tibolone on Breast Cancer Cell Proliferation in Postmenopausal ER+ Patients: Results from STEM Trial

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.

Therapy for Menopausal Symptoms During and After Treatment for Breast Cancer

Breast cancer is the most common newly diagnosed cancer in women. Life-time risk in the US is 1 in 8 (13.2%), in the UK it is 1 in 9 and in Australia it affects 1 in 11 women, of whom approximately 27% will be premenopausal at the time of their diagnosis. Many of these women will experience a sudden menopause as a result of chemotherapy, endocrine therapy or surgical interventions. For these women, the onset of menopausal symptoms is often sudden and severe. The management of such symptoms remains controversial. Women experiencing menopausal symptoms after breast cancer should be encouraged to avoid identifiable triggers for their symptoms and to consider lifestyle modification as a means of controlling those symptoms. When such measures fail, non-hormonal treatments may also be considered. These include clonidine, gabapentin and some antidepressants. Randomised trials have shown a significant difference in the symptom relief associated with various selective serotonin reuptake inhibitors and selective serotonin and noradrenaline (norepinephrine) reuptake inhibitors compared with placebo. Many women elect to use non-prescription complementary therapies to alleviate their menopausal symptoms. Systematic reviews of phytoestrogens have, however, failed to demonstrate significant relief of menopausal symptoms. More than 20 clinical trials have been conducted examining the relationship between postmenopausal hormone replacement therapy and breast cancer recurrence. The majority of these have been observational and have shown no increased risk of recurrence. However, the largest randomised trial that has thus far been conducted was recently halted because of a reported increase in the risk of recurrence amongst users of hormone replacement therapy. Tibolone, a selective tissue estrogen activity regulator, is a compound that exerts clinical effects both by receptor-mediated actions and tissue selective enzyme inhibition, and has been shown in preclinical studies to have different effects to estrogen on the breast. Although tibolone may prove safer than estrogen for long-term use in breast cancer survivors, the results of a large randomised trial are awaited to confirm this.The decision on how best to manage menopausal symptoms must thus be made on an individual basis and after thorough discussion and evaluation of the risks and benefits of each potential intervention.