The effects of bazedoxifene on mammographic breast density in postmenopausal women with osteoporosis

A comprehensive review on anticancer mechanism of bazedoxifene

Cancer is counted as a second leading cause of death among nontransmissible diseases. Identification of novel anticancer drugs is therefore necessary for the effective treatment of cancer. Conventional drug discovery is time consuming and expensive process. Unlike conventional drug discovery, drug repositioning offers a novel strategy for urgent drug discovery since it is a cost-effective and faster process. Bazedoxifene (BZA) is a synthetic selective estrogen receptor modulator, approved by the United States Food and Drug Administration for the treatment of osteoporosis in postmenopausal women. BZA is now being studied for its anticancer activity in various cancers including breast cancer, liver cancer, pancreatic cancer, colon cancer, head and neck cancer, medulloblastoma, brain cancer, and gastrointestinal cancer. Studies have reported that BZA is effective in reducing cancer progression through multiple mechanisms. BZA could effectively inhibit STAT3, PI3K/AKT, and MAPK signaling pathways and induce apoptosis. In addition to its anticancer activity as monotherapy, BZA has been shown to enhance the chemotherapeutic efficacy of clinical drugs such as paclitaxel, cisplatin, palbociclib, and oxaliplatin in multiple neoplasms. This review mainly focused on the anticancer activity, cellular targets, and anticancer mechanism of BZA, which may help the further design and conduct of research and repositioning it for oncological clinic trials.

Current Evidence of the Oncological Benefit-Risk Profile of Hormone Replacement Therapy

Hormone replacement therapy (HRT) remains the most effective treatment for menopausal symptoms and has been shown to prevent bone loss and fracture. The progestogen is added to provide endometrial protection in women with an intact uterus. After the publication of the initial WHI (Women's Health Initiative) results in 2002 reporting an overall increased risk of breast cancer, many women discontinued HRT. Despite the re-analysis of the results by subgroups of patients and updates with extended follow-up, much controversy remains, which we will analyze later in the text. Different types of estrogen or progestogen, as well as different formulations, doses, and durations, may play a role in HRT's effects on breast tissue. Evidence states that conjugated equine estrogen (CEE), compared to estro-progestin therapy, shows a better profile risk (HR 0.79, CI 0.65-0.97) and that, among different type of progestins, those structurally related to testosterone show a higher risk (RR 3.35, CI 1.07-10.4). Chronic unopposed endometrial exposure to estrogen increases the risk of endometrial hyperplasia and cancer, whereas the association with progestins, especially in continuous combined regimen, seems to reduce the risk (RR 0.71, CI 0.56-0.90). HRT was also associated with a protective effect on colon cancer risk (HR 0.61, CI 0.42-0.87). Data about ovarian and cervical cancer are still controversial.

Endometrial Cancer-Associated FGF18 Expression Is Reduced by Bazedoxifene in Human Endometrial Stromal Cells In Vitro and in Murine Endometrium

Endometrial cancer develops during exposure to estrogen unopposed by progesterone. Traditional formulations for menopausal hormone therapy include a progestin in women with a uterus. However, progestin exposure increases breast cancer risk in postmenopausal women. Alternatives to progestin include bazedoxifene (BZA), a selective estrogen receptor modulator, which prevents estrogen induced endometrial hyperplasia in clinical trials. Molecular mechanisms responsible for BZA's antiproliferative effect are not fully elucidated. We profiled endometrial adenocarcinoma, hyperplasia, and normal proliferative endometrium for differential expression in genes known to be regulated by estrogens or progesterone. Fibroblast growth factor (FGF)18, a paracrine growth factor promoting epithelial proliferation, was significantly increased in adenocarcinoma. Progesterone represses FGF18 by inducing heart and neural crest derivatives expressed transcript 2 (HAND2) in stromal cells. Notably, we confirmed lower HAND2 mRNA in adenocarcinoma, along with higher FGF tyrosine kinase receptor 2 and E74-like factor 5, collectively promoting FGF18 activity. We hypothesized BZA reduces epithelial proliferation by inhibiting FGF18 synthesis in stromal cells. To determine whether BZA regulates FGF18, we treated primary stromal cells with BZA or vehicle. In vitro, BZA reduced FGF18, but did not affect, HAND2. CD1 female mice received either BZA, conjugated estrogen (CE), or combined BZA/CE for 8 weeks. CE-treated mice had nearly 3-fold higher FGF18 expression. In contrast, BZA-treated mice, alone or with CE, had similar FGF18 as controls. Unexpectedly, BZA, alone or with CE, reduced HAND2 more than 80%, differing from progesterone regulation. Reduction of FGF18 is a potential mechanism by which BZA reduces endometrial proliferation and hyperplasia induced by estrogens. However, BZA works independently of HAND2, revealing a novel mechanism for progestin-free hormone therapy in postmenopausal women.

Relationship Between Breast Density and Selective Estrogen-Receptor Modulators, Aromatase Inhibitors, Physical Activity, and Diet: A Systematic Review

Background Lower breast density (BD) is associated with lower risk of breast cancer and may serve as a biomarker for the efficacy of chemopreventive strategies. This review explores parameters that are thought to be associated with lower BD. We conducted a systematic review of articles published to date using the PRISMA strategy. Articles that assessed change in BD with estrogen-receptor modulators (tamoxifene [TAM], raloxifene [RLX], and tibolone) and aromatase inhibitors (AIs), as well as cross-sectional and longitudinal studies (LSs) that assessed association between BD and physical activity (PA) or diet were reviewed. Results Ten studies assessed change in BD with TAM; all reported TAM-mediated BD decreases. Change in BD with RLX was assessed by 11 studies; 3 reported a reduction in BD. Effect of tibolone was assessed by 5 RCTs; only 1 reported change in BD. AI-mediated BD reduction was reported by 3 out of 10 studies. The association between PA and BD was assessed by 21 studies; 4 reported an inverse association. The relationship between diet and BD was assessed in 34 studies. All studies on calcium and vitamin D as well as vegetable intake reported an inverse association with BD in premenopausal women. Two RCTs demonstrated BD reduction with a low-fat, high-carbohydrate intervention. Conclusion TAM induces BD reduction; however, the effect of RLX, tibolone, and AIs on BD is unclear. Although data on association between diet and BD in adulthood are contradictory, intake of vegetables, vitamin D, and calcium appear to be associated with lower BD in premenopausal women.

Effects of ospemifene on the female reproductive and urinary tracts: translation from preclinical models into clinical evidence

Objective

Treatment of menopausal symptoms by compounds with tissue-selective estrogen agonist/antagonist effects, often called selective estrogen receptor modulators, has been researched as an alternative to the use of estrogen therapy. These structurally diverse molecules elicit tissue-dependent responses in hormone-responsive tissues and organs, exhibiting variations in estrogenic activity in preclinical models of postmenopausal reproductive tissues that may improve postmenopausal women’s health (eg, prevention and treatment of breast cancer, osteoporosis, and vulvar and vaginal atrophy).

Methods

This literature review investigates whether preclinical data predicted the clinical effects of ospemifene on female reproductive and urinary tract tissues and compares these findings with the specific vaginal effects of other estrogen receptor agonists/antagonists (tamoxifen, raloxifene, and bazedoxifene) in preclinical and clinical studies. Lasofoxifene, although not currently available, is included because of its unique effects on vaginal tissue.

Results

The response of endometrial and vaginal tissues to estrogen receptor agonists/antagonists can be differentiated using transvaginal ultrasound, endometrial histopathology, cytologic examination of vaginal smears, assessment of physical changes in the vagina, and relief of symptoms associated with vulvar and vaginal atrophy (such as dyspareunia).

Conclusions

Available evidence indicates that ospemifene has unique effects on tissue, leading to a favorable long-term profile for the relief of vulvar and vaginal atrophy compared with other estrogen receptor agonists/antagonists (eg, tamoxifen, raloxifene, and bazedoxifene) with no short-term concerns about endometrial safety (based on endometrial hyperplasia, carcinoma, endometrial spotting, and endometrial bleeding).

Bazedoxifene, a new orphan drug for the treatment of bleeding in hereditary haemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia (HHT), or Rendu-Osler-Weber syndrome, is a dominant genetic vascular disorder. In HHT, blood vessels are weak and prone to bleeding, leading to epistaxis and anaemia, severely affecting patients' quality of life. Development of vascular malformations in HHT patients is originated mainly by mutations in ACVRL1/ALK1 (activin receptor-like kinase type I) or Endoglin (ENG) genes. These genes encode proteins of the TGF-β signalling pathway in endothelial cells, controlling angiogenesis. Haploinsufficiency of these proteins is the basis of HHT pathogenicity. It was our objective to study the efficiency of Bazedoxifene, a selective estrogen receptor modulator (SERM) in HHT, looking for a decrease in epistaxis, and understanding the underlying molecular mechanism. Plasma samples of five HHT patients were collected before, and after 1 and 3 months of Bazedoxifene treatment. ENG and ALK1 expression in activated mononuclear cells derived from blood, as well as VEGF plasma levels, were measured. Quantification of Endoglin and ALK1 mRNA was done in endothelial cells derived from HHT and healthy donors, after in vitro treatment with Bazedoxifene. Angiogenesis was also measured by tubulogenesis and wound healing assays. Upon Bazedoxifene treatment, haemoglobin levels of HHT patients increased and the quantity and frequency of epistaxis decreased. Bazedoxifene increased Endoglin and ALK1 mRNA levels, in cells derived from blood samples and in cultured endothelial cells, promoting tube formation. In conclusion, Bazedoxifene seems to decrease bleeding in HHT by partial compensation of haploinsufficiency. The results shown here are the basis of a new orphan drug designation for HHT by the European Medicine Agency (EMA).

Selective estrogen receptor modulators and the combination therapy conjugated estrogens/bazedoxifene: A review of effects on the breast

Traditional menopausal hormone therapy containing estrogens/progestin has been associated with an increased risk of breast cancer, and estrogen exposure is known to promote growth and proliferation of a majority of breast cancers. Therefore, it is important for clinicians to consider the breast safety profile of any hormone-based therapy used in postmenopausal women. This review provides an overview of the breast safety and tolerability profiles of currently marketed selective estrogen receptor modulators, antiestrogens, and the first tissue selective estrogen complex combining conjugated estrogens with the selective estrogen receptor modulator bazedoxifene in postmenopausal women. Selective estrogen receptor modulators and antiestrogens act as estrogen receptor antagonists in the breast. Tamoxifen, toremifene, and the selective estrogen receptor degrader fulvestrant are used to treat breast cancer, and tamoxifen and raloxifene protect against breast cancer in high-risk women. Postmenopausal women using selective estrogen receptor modulators for prevention or treatment of osteoporosis (raloxifene, bazedoxifene) can be reassured that these hormonal treatments do not adversely affect their risk of breast cancer and may, in the case of raloxifene, even be protective. There are limited data on breast cancer in women who use ospemifene for dyspareunia. Conjugated estrogens/bazedoxifene use for up to two years did not increase mammographic breast density or breast pain/tenderness, and there was no evidence of an increased risk of breast cancer, suggesting that conjugated estrogens/bazedoxifene has an improved breast safety profile compared with traditional menopausal hormone therapies. Future research will continue to focus on development of selective estrogen receptor modulators and selective estrogen receptor modulator combinations capable of achieving the ideal balance of estrogen receptor agonist and antagonist effects.

Incorporating bazedoxifene into the treatment paradigm for postmenopausal osteoporosis in Japan

The incidence of osteoporosis-related fractures in Asian countries is steadily increasing. Optimizing osteoporosis treatment is especially important in Japan, where the rate of aging is increasing rapidlyelderly population is increasing rapidly and life expectancy is among the longest in the world. There are several therapies currently available in Japan for the treatment of postmenopausal osteoporosis, each with a unique risk/benefit profile. A novel selective estrogen receptor modulator, bazedoxifene (BZA), was recently approved for the treatment of postmenopausal osteoporosis in Japan. Results from a 2-year, phase 2 trial in postmenopausal Japanese women showed that BZA significantly improved lumbar spine and total hip bone mineral density compared with placebo, while maintaining endometrial and breast safety, consistent with results from 2 global, phase 3 trials including a 2-year osteoporosis prevention study and a 3-year osteoporosis treatment study. In the pivotal 3-year treatment study, BZA significantly reduced the incidence of new vertebral fractures compared with placebo; in a post hoc analysis of a subgroup of women at higher risk of fractures, BZA significantly reduced the risk of nonvertebral fractures compared with placebo and raloxifene. A 2-year extension of the 3-year treatment study demonstrated the sustained efficacy of BZA over 5 years of treatment. BZA was generally safe and well tolerated in these studies. In a "super-aging" society such as Japan, long-term treatment for postmenopausal osteoporosis is a considerable need. BZA may be considered as a first choice for younger women anticipating long-term treatment, and also an appropriate option for older women who are unable or unwilling to take bisphosphonates.

Efficacy and safety of currently marketed anti-osteoporosis medications

During the past 2 decades, many interventions were proven effective in the management of postmenopausal osteoporosis. The objective of an anti-osteoporosis treatment is to reduce fracture rates, ideally at all skeletal sites (i.e. spine, hip, and other non-spine). The armamentarium against osteoporosis includes anti-resorptive agents (i.e. bisphosphonates, selective estrogen receptor modulators and denosumab), bone-forming agents (i.e. peptides from the parathyroid hormone family) and one agent with a dual mechanism of action (i.e. strontium ranelate). All these medications combine antifracture efficacy with a reasonable benefit/risk profile. However, the choice of a particular chemical entity, in one individual patient is based on the knowledge and expertise of the physician. Prioritization of drugs should be based on the individual profile of the patient, the severity of osteoporosis and the specific contraindications, warnings and precautions of use of the various available medications.

From empirical to mechanism-based discovery of clinically useful Selective Estrogen Receptor Modulators (SERMs)

Our understanding of the molecular mechanisms underlying the pharmacological actions of estrogen receptor (ER) ligands has evolved considerably in recent years. Much of this knowledge has come from a detailed dissection of the mechanism(s) of action of the Selective Estrogen Receptor Modulators (SERMs) tamoxifen and raloxifene, drugs whose estrogen receptor (ER) agonist/antagonist properties are influenced by the cell context in which they operate. These studies have revealed that notwithstanding differences in drug pharmacokinetics, the activity of an ER ligand is determined primarily by (a) the impact that a given ligand has on the receptor conformation and (b) the ability of structurally distinct ER-ligand complexes to interact with functionally distinct coregulators. Exploitation of the established relationships between ER structure and activity has led to the development of improved SERMs with more favorable therapeutic properties and of tissue-selective estrogen complexes, drugs in which a SERM and an ER agonist are combined to yield a blended activity that results in distinct clinical profiles. Remarkably, endogenous ligands that exhibit SERM activity have also been identified. One of these ligands, 27-hydroxycholesterol (27HC), has been shown to manifest ER-dependent pathological activities in the cardiovascular system, bone and mammary gland. Whereas the physiological activity of 27HC remains to be determined, its discovery highlights how cells have adopted mechanisms to allow the same receptor ligand complex to manifest different activities in different cells, and also how these processes can be exploited for new drug development.

Conjugated estrogen/bazedoxifene tablets for the treatment of moderate-to-severe vasomotor symptoms associated with menopause

Conjugated estrogen/bazedoxifene (CE/BZA) therapy represents a new, progestin-free treatment in the management of postmenopausal health. CE/BZA pairs CE with the selective estrogen receptor modulator, BZA. The rationale for the development of CE/BZA was that BZA, acting primarily as a selective estrogen receptor degrader in uterine and breast tissue, would sufficiently inhibit the proliferative effects of CE on the endometrium. The absence of a progestin would reduce the incidence of uterine bleeding, breast pain and increased breast density associated with progestin-containing hormone therapy. CE/BZA has been evaluated in five multicenter, randomized, double-blind, placebo-controlled, and active-controlled Phase III trials known as the SMART trials. CE/BZA has been shown to maintain the established benefits of estrogen therapy for treatment of vasomotor symptoms and prevention of a loss in bone mineral density (bone mass), while minimizing certain estrogenic effects, particularly in the uterine endometrium and breast.

Selective estrogen receptor modulators: tissue specificity and clinical utility

Selective estrogen receptor modulators (SERMs) are a diverse group of nonsteroidal compounds that function as agonists or antagonists for estrogen receptors (ERs) in a target gene-specific and tissue-specific fashion. SERM specificity involves tissue-specific expression of ER subtypes, differential expression of co-regulatory proteins in various tissues, and varying ER conformational changes induced by ligand binding. To date, the major clinical applications of SERMs are their use in the prevention and treatment of breast cancer, the prevention of osteoporosis, and the maintenance of beneficial serum lipid profiles in postmenopausal women. However, SERMs have also been found to promote adverse effects, including thromboembolic events and, in some cases, carcinogenesis, that have proven to be obstacles in their clinical utility. In this review, we discuss the mechanisms of SERM tissue specificity and highlight the therapeutic application of well-known and emergent SERMs.

Breast-related effects of selective estrogen receptor modulators and tissue-selective estrogen complexes

A number of available treatments provide relief of menopausal symptoms and prevention of postmenopausal osteoporosis. However, as breast safety is a major concern, new options are needed, particularly agents with an improved mammary safety profile. Results from several large randomized and observational studies have shown an association between hormone therapy, particularly combined estrogen-progestin therapy, and a small increased risk of breast cancer and breast pain or tenderness. In addition, progestin-containing hormone therapy has been shown to increase mammographic breast density, which is an important risk factor for breast cancer. Selective estrogen receptor modulators (SERMs) provide bone protection, are generally well tolerated, and have demonstrated reductions in breast cancer risk, but do not relieve menopausal symptoms (that is, vasomotor symptoms). Tissue-selective estrogen complexes (TSECs) pair a SERM with one or more estrogens and aim to blend the positive effects of the components to provide relief of menopausal symptoms and prevention of postmenopausal osteoporosis without stimulating the breast or endometrium. One TSEC combination pairing conjugated estrogens (CEs) with the SERM bazedoxifene (BZA) has completed clinical development and is now available as an alternative option for menopausal therapy. Preclinical evidence suggests that CE/BZA induces inhibitory effects on breast tissue, and phase 3 clinical studies suggest breast neutrality, with no increases seen in breast tenderness, breast density, or cancer. In non-hysterectomized postmenopausal women, CE/BZA was associated with increased bone mineral density and relief of menopausal symptoms, along with endometrial safety. Taken together, these results support the potential of CE/BZA for the relief of menopausal symptoms and prevention of postmenopausal osteoporosis combined with breast and endometrial safety.

Current challenges in the treatment of osteoporosis: an opportunity for bazedoxifene

BACKGROUND

Osteoporosis affects millions of postmenopausal women worldwide. Osteoporosis-related fractures can lead to chronic pain, disability, systemic complications, and increased risk of recurrent fractures, resulting in increased healthcare costs and mortality. Because currently available therapies have unique benefit/risk profiles, challenges remain in selecting the most appropriate treatment for each osteoporotic woman. RESEARCH AND RESULTS: Bazedoxifene (BZA), a new selective estrogen receptor modulator, is being developed for postmenopausal osteoporosis. In a 3 year, global, phase 3 study, BZA significantly reduced the risk of new vertebral fractures and nonvertebral fractures in women with higher baseline fracture risk compared with placebo. In two extensions of this study, the efficacy of BZA in reducing vertebral fracture risk was sustained over 7 years. BZA improved lumbar spine and total hip bone mineral density compared with placebo at 3 and 5 years, and demonstrated a favorable safety/tolerability profile, with no endometrial or breast stimulation. BZA was cost-effective compared with raloxifene in a 3 year, head-to-head comparative trial. Indirect comparisons further suggest that BZA may be as effective as bisphosphonates in reducing risk of nonvertebral fractures in women at high risk of fracture. BZA demonstrated efficacy and safety for treating postmenopausal osteoporosis over 7 years, particularly in women at a higher fracture risk.

CONCLUSION

Because of its specific pharmacologic profile, BZA may be appropriate for postmenopausal women seeking a tolerable, safe, effective, and cost-effective long-term osteoporosis treatment.

Smaller reduction in 3D breast density associated with subsequent cancer recurrence in patients with breast cancer receiving adjuvant tamoxifen therapy

OBJECTIVE

The purpose of this study was to retrospectively investigate whether 3D breast density changes measured using MRI were associated with recurrent cancer in patients with breast cancer who received adjuvant tamoxifen.

MATERIALS AND METHODS

A search of the breast MRI database (2007-2008) revealed a dataset that included 80 women (mean age, 44 years; range, 27-68 years) with breast cancer who underwent breast-conserving surgery, adjuvant tamoxifen treatment, and breast MRI before and after tamoxifen. The following clinicopathologic variables were collected: age, body mass index, menopausal status, family history, tumor stage, tumor grade, hormonal receptor status, and adjuvant chemotherapy status. MRI variables (total breast volume, fibro-glandular volume, and breast density) were measured for the contralateral untreated breast before and after tamoxifen treatment, and the percentage changes were recorded. A multivariate logistic regression analysis was performed to identify independent factors that were associated with cancer recurrence.

RESULTS

Overall, 12 (15%) of the 80 women developed recurrence. No recurrent cancers were found in the remaining 68 patients (85%) at a median follow-up of 48 months (range, 37-60 months). Percentage reduction of breast density after tamoxifen was the only independent factor associated with recurrence (adjusted odds ratio [OR] = 0.848, 95% CI = 0.769-0.935, and p = 0.001 for observer 1; adjusted OR = 0.957, 95% CI = 0.919-0.996, and p = 0.032 for observer 2) in the multivariate analysis.

CONCLUSION

Three-dimensional breast density changes measured using MRI during tamoxifen treatment were an independent factor associated with cancer recurrence in patients with breast cancer who received adjuvant tamoxifen.

Effect of preventive hormonal therapy on breast density: a systematic qualitative review

Breast density (BD) is recognized as one of the strongest independent risk factors of breast cancer (BC). Unlike most other risk factors, BD can be modified, suggesting that it may be a biomarker for preventive interventions. We conducted a qualitative systematic review to address the effect of preventive hormonal therapy on BD. Among the 26 relevant studies, 10 assessed the effect of tamoxifen on BD (TAM: n = 2 877), 9 that of raloxifene (RLX: n = 1 544), and 7 that of aromatase inhibitors (AI: n = 416). The studies were characterized by a large heterogeneity in designs and in methods of BD measurement. BD could be reduced by TAM (10 studies/10). However, the effect of RLX and AI on BD remains unclear due to conflicting results between studies. Consequently, it is crucial to develop practical, accurate, and reproducible methods of measurement in order to be able to compare the effect of preventive hormonal agents on BD and to determine whether change in BD can be used as a predictor of response to therapy.

Effects of menopausal hormonal therapy on occult breast tumors

An estimated 7% of 40-80 year old women dying of unrelated causes harbor occult breast tumors at autopsy. These lesions are too small to be detected by mammography, a method which requires tumors to be approximately 1cm in diameter to be diagnosed. Tumor growth rates, as assessed by "effective doubling times" on serial mammography range from 10 to >700 days with a median of approximately 200 days. We previously reported two models, based on iterative analysis of these parameters, to describe the biologic behavior of undiagnosed, occult breast tumors. One of our models is biologically based and includes parameters of a 200 day effective doubling time, 7% prevalence of occult tumors in the 40-80 aged female population and a detection threshold of 1.16 cm and the other involves computer based projections based on age related breast cancer incidence. Our models facilitate interpretation of the Women's Health Initiative (WHI) and anti-estrogen prevention studies. The biologically based model suggests that menopausal hormone therapy with conjugated equine estrogens plus medroxyprogesterone acetate (MPA) in the WHI trial primarily promoted the growth of pre-existing, occult lesions and minimally initiated de novo tumors. The paradoxical reduction of breast cancer incidence in women receiving estrogen alone is consistent with a model that this hormone causes apoptosis in women deprived of estrogen long term as a result of the cessation of estrogen production after the menopause. Understanding of the kinetics of occult tumors suggests that breast cancer "prevention" with anti-estrogens or aromatase inhibitors represents early treatment rather than a reduction in de novo tumor formation. Our in vivo data suggest that the combination of a SERM, bazedoxifene (BZA), with conjugated equine estrogen (CEE) acts to block maturation of the mammary gland in oophorectomized, immature mice. This hormonal combination is defined by the generic term, tissue selective estrogen complex or TSEC. Xenograft studies with the BZA/CEE combination show that it blocks the growth of occult, hormone dependent tumors in nude mice. These pre-clinical data suggest that the BZA/CEE TSEC combination may prevent the growth of occult breast tumors in women. Based on the beneficial effects of this TSEC combination on symptoms and fracture prevention in menopausal women, the combination of BZA/CEE might be used as a means both to treat menopausal symptoms and to prevent breast cancer. This article is part of a Special Issue entitled 'CSR 2013'.

Vitamin D supplementation and breast cancer prevention: a systematic review and meta-analysis of randomized clinical trials

In recent years, the scientific evidence linking vitamin D status or supplementation to breast cancer has grown notably. To investigate the role of vitamin D supplementation on breast cancer incidence, we conducted a systematic review and meta-analysis of randomized controlled trials comparing vitamin D with placebo or no treatment. We used OVID to search MEDLINE (R), EMBASE and CENTRAL until April 2012. We screened the reference lists of included studies and used the “Related Article” feature in PubMed to identify additional articles. No language restrictions were applied. Two reviewers independently extracted data on methodological quality, participants, intervention, comparison and outcomes. Risk Ratios and 95% Confident Intervals for breast cancer were pooled using a random-effects model. Heterogeneity was assessed using the I² test. In sensitivity analysis, we assessed the impact of vitamin D dosage and mode of administration on treatment effects. Only two randomized controlled trials fulfilled the pre-set inclusion criteria. The pooled analysis included 5372 postmenopausal women. Overall, Risk Ratios and 95% Confident Intervals were 1.11 and 0.74–1.68. We found no evidence of heterogeneity. Neither vitamin D dosage nor mode of administration significantly affected breast cancer risk. However, treatment efficacy was somewhat greater when vitamin D was administered at the highest dosage and in combination with calcium (Risk Ratio 0.58, 95% Confident Interval 0.23–1.47 and Risk Ratio 0.93, 95% Confident Interval 0.54–1.60, respectively). In conclusions, vitamin D use seems not to be associated with a reduced risk of breast cancer development in postmenopausal women. However, the available evidence is still limited and inadequate to draw firm conclusions. Study protocol code: FARM8L2B5L.

Effects of bazedoxifene acetate with and without conjugated equine estrogens on the breast of postmenopausal monkeys

OBJECTIVE

Concerns about increased breast cancer risk with estrogen and progestin therapy have led to an increased interest in progestin alternatives. The main objective of this study was to determine if bazedoxifene acetate (BZA), a new selective estrogen receptor modulator, will antagonize the proliferative and transcriptional effects of conjugated equine estrogens (CEE) in the breast.

METHODS

As part of a 20-month preclinical trial, 95 ovariectomized cynomolgus macaques (Macaca fascicularis) were randomized to receive no treatment or treatment with BZA (20 mg/d), CEE (0.45 mg/d), or BZA and CEE in combination (women's daily equivalent doses). The data presented here include breast effects after 6 months of treatment. Endpoints included histomorphometry, histopathological evaluations, gene microarray assays, polymerase chain reaction quantification of specific estrogen receptor α (ER-α) activity markers, and immunohistochemical detection of sex steroid receptors, and the proliferation marker Ki67.

RESULTS

BZA + CEE and BZA resulted in significantly less total epithelial density, lobular enlargement, and Ki67 immunolabeling in the terminal ducts compared with CEE alone (P < 0.05 for all). The addition of BZA to CEE antagonized the expression of ER-α-regulated genes such as GREB1 and TFF1 (P < 0.01 for both), whereas BZA alone had minimal effects on ER-α-mediated transcriptional activity. BZA and BZA + CEE did not significantly up-regulate genes related to cell cycle progression and proliferation. BZA with and without CEE also resulted in less lobular and terminal duct ER-α immunolabeling compared with control and CEE (P < 0.0001 for all).

CONCLUSIONS

These findings demonstrate that BZA given at a clinically relevant dose is an estrogen antagonist in the breast, supporting the idea that CEE + BZA may provide a lower breast cancer risk profile compared with traditional estrogen + progestin therapies.

Nuclear receptors and their selective pharmacologic modulators

Nuclear receptors are ligand-activated transcription factors and include the receptors for steroid hormones, lipophilic vitamins, sterols, and bile acids. These receptors serve as targets for development of myriad drugs that target a range of disorders. Classically defined ligands that bind to the ligand-binding domain of nuclear receptors, whether they are endogenous or synthetic, either activate receptor activity (agonists) or block activation (antagonists) and due to the ability to alter activity of the receptors are often termed receptor "modulators." The complex pharmacology of nuclear receptors has provided a class of ligands distinct from these simple modulators where ligands display agonist/partial agonist/antagonist function in a tissue or gene selective manner. This class of ligands is defined as selective modulators. Here, we review the development and pharmacology of a range of selective nuclear receptor modulators.

Inhibitory effects of a bazedoxifene/conjugated equine estrogen combination on human breast cancer cells in vitro

Breast cancer incidence is increased in women receiving menopausal hormone therapy with estrogen plus progestin but not with estrogen alone. The use of a tissue-selective estrogen complex (TSEC) has been proposed as a novel menopausal hormone therapy strategy to eliminate the requirement for a progestogen. Combination of bazedoxifene (BZA) with conjugated estrogens (CEs), the first TSEC, has shown beneficial effects. Whether it would exert antiestrogenic effects on breast cancer is not clear. To address this issue, we compared estradiol (E(2)) and CE alone on proliferation and apoptosis in MCF-7 breast cancer cells. CE stimulated growth of MCF-7 cells at a peak concentration 10-fold higher than required for E(2). Both CE and E(2) alone increased DNA synthesis and reduced apoptosis with activation of MAPK, Akt, and p70S6K and up-regulation of antiapoptotic factors survivin, Bcl-2, and X-linked inhibitor of apoptosis protein, These effects could be completely blocked by BZA. Gene expression studies demonstrated that CE and E(2) were equally potent on expression of cMyc, pS2, and WNT1 inducible signaling pathway protein 2, whereas the stimulatory effects of CE on progesterone receptor and amphiregulin expression were weaker than E(2). BZA effectively blocked each of these effects and showed no estrogen agonistic effects when used alone. Our results indicate that the stimulatory effects of E(2) or CE on breast cancer cells could be completely abrogated by BZA. These studies imply that the CE/BZA, TSEC, exerts antiestrogenic effects on breast cancer cells and might block the growth of occult breast neoplasms in postmenopausal women, resulting in an overall reduction in tumor incidence.

[Third generation selective estrogen receptor modulators benefits beyond bone: effects on breast]

The selective estrogen receptor modulators (SERMs) are substances with estrogenic/anti-estrogen effect that act differently depending on the tissue and composition. Since the discovery that tamoxifen and raloxifene (RLX) had a breast cancer preventive effect, the search for the perfect SERM has been the goal. Thus, ospemifen, arzoxifene, lasofoxifene and bazedoxifene (BZA) appeared as third-generation SERMs. Among all them, only BZA reached the stage of clinical use. BZA has been shown to have an anti-estrogen effect in experimental studies, but not a protective effect on clinical breast cancer in pivotal clinical trials (301 and extensions). However, in these studies comparing BZA versus RLX and placebo, RLX has not shown the expected preventive effect on breast cancer. This lack of effect can be the consequence of the size and characteristics of BZA's studies in a population with low incidence of breast cancer.

Effects of the conjugated equine estrogen/bazedoxifene tissue-selective estrogen complex (TSEC) on mammary gland and breast cancer in mice

A tissue-selective estrogen complex (TSEC), combining a selective estrogen receptor modulator, bazedoxifene (BZA), with conjugated equine estrogen (CEE), represents a novel strategy of menopausal hormone therapy without involving a progestin. We hypothesized that the antiestrogenic properties of BZA can also block the estrogenic effects of CEE on breast tissue and thereby prevent breast cancer in women. To test our hypothesis, the effects of estradiol (E(2)), CEE, and BZA on mammary gland and breast cancer xenografts were assessed in mouse models. In immature castrate mice, BZA completely blocked CEE- or E(2)-stimulated ductal and terminal end bud growth of mammary gland as well as estrogen-responsive gene expression. As a positive control, E(2) stimulated tumor growth in nude mice bearing MCF-7 xenografts. This effect was completely blocked by BZA as were E(2)-stimulated expression of PR, pS2 (trefoil factor 1), cMyc, and AREG; the enhancement of Ki67 and proliferating cell nuclear antigen (PCNA); and the antiapoptotic effect. CEE was much less potent than E(2) in stimulating Ki67, reducing apoptosis, and stimulating gene expression, but all effects were blocked by BZA. Unexpectedly, CEE alone, even at high doses, did not stimulate tumor growth. As confirmation of its absorption and deconjugation, CEE caused a 6-fold increase in uterine weight and stimulation of gene expression. These data support our hypothesis that the net effect of the CEE/BZA TSEC is to block estrogen action in benign and malignant breast tissue. These findings provide a rationale for a clinical study to determine whether this TSEC prevents breast cancer in women.

Relationships between changes in bone mineral density or bone turnover markers and vertebral fracture incidence in patients treated with bazedoxifene

We analyzed the relationships between bone mineral density (BMD) or bone turnover marker (BTM) changes and vertebral fracture incidence in women treated with bazedoxifene using a post hoc analysis from a 3-year randomized, placebo-controlled study evaluating the effect of bazedoxifene (20 or 40 mg) on fracture risk reduction. BMD was assessed at baseline and every 6 months for 3 years. Osteocalcin and C-telopeptide of type I collagen were assessed at baseline and at 3, 12, and 36 months. Vertebral fractures were assessed with a semiquantitative visual assessment. Data were available for 5,244 women, of whom 3,476 were treated with bazedoxifene. Using a logistic regression analysis and the classical Li approach, the proportion of fracture incidence explained by BMD change after 3 years of bazedoxifene treatment was 29 % for the total hip and 44 % for the femoral neck. The proportion of treatment explained by lumbar BMD change could not be quantified accurately because of the significant interaction between treatment and change in BMD. With the same model, the 12-month BTM changes explained up to 29 % of the fracture risk reduction observed with the two forms of bazedoxifene. In women treated with bazedoxifene, changes in femoral neck BMD, hip BMD, or BTMs explained a moderate proportion of the fracture risk reduction observed during the 3 years of follow-up. However, BMD or BTM changes cannot be recommended for individual monitoring of women treated with bazedoxifene.

The tissue selective estrogen complex: a promising new menopausal therapy

Menopause is associated with health concerns including vasomotor symptoms, vulvar/vaginal atrophy (VVA), and osteoporosis. Estrogen therapy or combined estrogen-progestin therapy (EPT) are primary treatment options for menopausal symptom relief and osteoporosis prevention. Because EPT has been associated with some safety/tolerability concerns relating to undesirable effects of estrogen and progestin, alternative options are needed. The tissue selective estrogen complex (TSEC) is a novel class of agents pairing a selective estrogen receptor modulator (SERM) with 1 or more estrogens. The TSEC combines the established efficacy of estrogens on menopausal symptoms and bone with the protective effects of a SERM on the reproductive tract. The pairing of bazedoxifene (BZA) with conjugated estrogens (CE) has been evaluated in a series of phase 3 clinical trials. BZA 20 mg/CE 0.45 mg and BZA 20 mg/CE 0.625 mg have shown efficacy in reducing the frequency and severity of hot flushes, relieving VVA symptoms, and maintaining bone mass while protecting the endometrium and breast. These BZA/CE doses have been associated with a favorable safety/tolerability profile, with higher rates of cumulative amenorrhea and lower incidences of breast pain than those reported for EPT. Thus, BZA/CE may be a promising alternative to conventional EPT for treating non-hysterectomized, postmenopausal women.

Bazedoxifene: the evolving role of third-generation selective estrogen-receptor modulators in the management of postmenopausal osteoporosis

Osteoporosis is a significant public health concern, particularly for postmenopausal women. Current treatment options may not be appropriate for all women. Selective estrogen-receptor modulators (SERMs) are a class of molecules with tissue-selective activity. Bazedoxifene is currently in clinical development for the prevention and treatment of postmenopausal osteoporosis. In a 2-year, phase III, osteoporosis prevention study (N = 1583), bazedoxifene 10, 20, and 40 mg was shown to preserve bone mineral density and decrease biochemical markers of bone turnover compared with placebo in postmenopausal women at risk for osteoporosis. In a pivotal 3-year, phase III, osteoporosis treatment study (N = 7492), bazedoxifene 20 and 40 mg significantly reduced the incidence of new vertebral fractures compared with placebo (p < 0.05 for both) in postmenopausal women with osteoporosis. In a post hoc subgroup analysis of women at higher risk for fracture (n = 1772), bazedoxifene 20 mg significantly reduced the risk of nonvertebral fractures versus placebo (p = 0.02) and raloxifene 60 mg (p = 0.05). Bazedoxifene 20 mg has demonstrated sustained efficacy in reducing the risk of vertebral fractures over 5 and 7 years. Overall, bazedoxifene was generally safe and well tolerated, with favorable endometrial and breast safety profiles. As with other SERMs, the rate of deep vein thrombosis was higher in the bazedoxifene groups compared with placebo at 3 and 5 years. Considering its demonstrated efficacy and safety, bazedoxifene may be an appropriate osteoporosis therapy for women who cannot take or are unwilling to take bisphosphonates because of safety or tolerability issues. Bazedoxifene may also be appropriate for younger women at increased fracture risk who are concerned about the effects of long-term bisphosphonate therapy. This article reviews the results of key clinical trials of bazedoxifene for the prevention and treatment of postmenopausal osteoporosis and describes its role in clinical practice.

Bazedoxifene: a review of its use in the treatment of postmenopausal osteoporosis

Bazedoxifene (Conbriza®, Viviant®) is the first third-generation selective estrogen receptor modulator (SERM) and it is approved for the treatment of postmenopausal osteoporosis in the EU and Japan. Bazedoxifene contains an indole-based core binding domain that binds with high affinity to estrogen receptors and exhibits favourable effects on bone and lipid profiles, with no clinically relevant endometrial or breast stimulation. Oral bazedoxifene once daily reduced the incidence of new vertebral fractures in patients with postmenopausal osteoporosis in a large, well designed trial of 3 years' duration; both bazedoxifene and raloxifene were significantly more effective than placebo. Neither bazedoxifene nor raloxifene reduced the incidence of nonvertebral fractures in the overall study population; however, bazedoxifene, but not raloxifene, reduced the rate of nonvertebral fractures in high-risk patients. Moreover, data from patients who continued to receive the drug during a 2-year extension phase of this trial indicate that bazedoxifene continues to provide protection against new vertebral fractures for up to 5 years. Bazedoxifene also increases bone mineral density and reduces the levels of bone turnover markers. Bazedoxifene was generally well tolerated and did not detrimentally affect the reproductive tract or breast tissue in clinical trials, thereby demonstrating a favourable risk-benefit profile. A pharmacoeconomic analysis conducted from an EU perspective predicted bazedoxifene to be cost effective in some EU countries. Therefore, bazedoxifene presents another useful option for the treatment of postmenopausal osteoporosis, especially in those at high risk for osteoporotic fracture.

Sustained efficacy and safety of bazedoxifene in preventing fractures in postmenopausal women with osteoporosis: results of a 5-year, randomized, placebo-controlled study

In this 2-year extension of a 3-year study, bazedoxifene showed sustained efficacy in preventing new vertebral fractures in postmenopausal women with osteoporosis and in preventing non-vertebral fractures in higher-risk women. Bazedoxifene significantly increased bone mineral density and reduced bone turnover versus placebo and was generally safe and well tolerated.

INTRODUCTION

This study evaluated the efficacy and safety of bazedoxifene for the treatment of postmenopausal osteoporosis over 5 years.

METHODS

A total of 4,216 postmenopausal women with osteoporosis were enrolled in this 2-year extension of a 3-year, randomized, double-blind, placebo-controlled, phase 3 trial. In the core study (N = 7,492), subjects received bazedoxifene 20 or 40 mg/day, raloxifene 60 mg/day, or placebo. The raloxifene arm was discontinued after 3 years; subjects receiving bazedoxifene 40 mg were transitioned to bazedoxifene 20 mg after 4 years. Five-year findings are reported for bazedoxifene 20 and 40/20 mg and placebo. Endpoints included incidence of new vertebral fractures (primary) and non-vertebral fractures, and changes in bone mineral density (BMD) and bone turnover markers.

RESULTS

At 5 years, the incidence of new vertebral fractures in the intent-to-treat population was significantly lower with bazedoxifene 20 mg (4.5%) and 40/20 mg (3.9%) versus placebo (6.8%; P < 0.05), with relative risk reductions of 35% and 40%, respectively. Non-vertebral fracture incidence was similar among groups. In a subgroup of higher-risk women (n = 1,324; femoral neck T-score ≤-3.0 and/or ≥ 1 moderate or severe or ≥ 2 mild vertebral fracture[s]), bazedoxifene 20 mg reduced non-vertebral fracture risk versus placebo (37%; P = 0.06); combined data for bazedoxifene 20 and 40/20 mg reached statistical significance (34% reduction; P < 0.05). Bazedoxifene significantly increased BMD and reduced bone turnover versus placebo (P < 0.05) and was generally safe and well tolerated.

CONCLUSIONS

The findings support a sustained anti-fracture effect of bazedoxifene on new vertebral fractures in postmenopausal osteoporotic women and on non-vertebral fractures in the higher-risk subgroup of women.

An update on selective estrogen receptor modulators for the prevention and treatment of osteoporosis

Several selective estrogen receptor modulators are in clinical development for postmenopausal osteoporosis. Bazedoxifene has shown significant reductions in vertebral and non-vertebral (in higher-risk women) fracture risk, with no evidence of breast or endometrial stimulation. Lasofoxifene has demonstrated significant reductions in vertebral and non-vertebral fracture risk, but has been associated with endometrial/uterine effects. Both selective estrogen receptor modulators were generally safe and well tolerated but have been associated with some "class effects" (e.g., hot flushes, venous thromboembolic events). A tissue selective estrogen complex partnering bazedoxifene with conjugated estrogens is under clinical investigation for the treatment of menopausal symptoms and osteoporosis prevention. Future directions in selective estrogen receptor modulator research include ospemifene and RAD 1901.

Prevention of osteoporosis: one step forward, two steps back

For many years, hormone replacement therapy (HRT) was the mainstay for osteoporosis prevention in postmenopausal women until a large randomized clinical trial raised serious safety concerns. This resulted in a big drop in HRT use and its demotion by regulatory authorities to second-line treatment. Many clinicians now feel that HRT is not safe to use, and recommend various alternatives for the treatment of osteoporosis. But how effective are these alternative therapies, are they any safer than HRT, and how do their costs compare? This review questions the validity of the safety concerns about HRT, and highlights the safety concerns about alternative therapies. It concludes that HRT is as safe as the other treatment options, and its efficacy and low cost demand that it be restored as a first-line treatment for the prevention of postmenopausal osteoporosis. Other therapies are available for use in osteoporosis, and the bisphosphonates are particularly effective for the treatment of the established disease. However, they must be used selectively and with caution, and are best restricted to those patients who are elderly or have severe disease. New treatments are emerging, but again caution must be taken until any long-term adverse effects have been identified.

Bazedoxifene: a new selective estrogen receptor modulator for postmenopausal osteoporosis

An ongoing need for safe and effective pharmacological therapies exists for postmenopausal osteoporosis, which imposes a significant burden on both women and the health-care system. Bazedoxifene is a novel selective estrogen receptor modulator with a unique tissue-selectivity profile. In phase 3 clinical trials of nearly 10,000 postmenopausal women, bazedoxifene was shown to significantly reduce the risk of new vertebral fracture versus placebo, with favourable effects on bone mineral density, bone turnover markers and the lipid profile. Moreover, in a subgroup of women at increased risk of fracture, bazedoxifene significantly decreased non-vertebral fracture risk versus both placebo and raloxifene. Bazedoxifene has been shown to be safe and well tolerated, with no evidence of endometrial or breast stimulation. These data suggest that bazedoxifene may offer significant clinical benefit for postmenopausal women with or at risk of developing osteoporosis, which may subsequently lessen the medical and economic burden of this disease.

Efficacy and safety of bazedoxifene for postmenopausal osteoporosis

Bazedoxifene, a novel selective estrogen receptor modulator, has been developed to have favorable effects on bone and the lipid profile while minimizing stimulation of uterine or breast tissues. Two large Phase III clinical trials showed that bazedoxifene, as well as raloxifene, increased bone mineral density, decreased levels of bone turnover markers, and significantly reduced the risk of new vertebral fractures in postmenopausal women compared with placebo. Although the incidence of nonvertebral fractures with bazedoxifene or raloxifene did not differ significantly from that with placebo, a post hoc analysis of a subgroup of women at higher fracture risk revealed that bazedoxifene significantly reduced the nonvertebral fracture risk relative to placebo and raloxifene. Bazedoxifene also improved the lipid profile by reducing the serum concentrations of total cholesterol and low-density lipoprotein cholesterol, with an increase in the serum level of high-density lipoprotein cholesterol. The incidences of vasodilatation (hot flushes), leg cramps, and venous thromboembolic events were significantly higher with bazedoxifene and raloxifene compared with placebo. There was no evidence of endometrial and breast stimulation with bazedoxifene. Taking advantage of the favorable effects of bazedoxifene on the breast and endometrium, the pairing of bazedoxifene with conjugated estrogens is under investigation for the treatment of menopausal symptoms and prevention of postmenopausal osteoporosis. A Phase III trial showed that combination therapy of bazedoxifene and conjugated estrogens significantly increased bone mineral density and decreased bone turnover markers, with relief of hot flushes and improvement of vaginal atrophy. This article reviews the clinical efficacy and safety of bazedoxifene in the treatment of postmenopausal osteoporosis.

Bazedoxifene: a novel selective estrogen receptor modulator for postmenopausal osteoporosis

Several new selective estrogen receptor modulators (SERMs) are currently under clinical development for the prevention and/or treatment of postmenopausal osteoporosis, with the goal of optimizing the estrogen receptor agonist/antagonist activity in target tissues. Bazedoxifene is a novel SERM under clinical investigation for the prevention and treatment of postmenopausal osteoporosis. Emerging clinical data have shown that bazedoxifene is effective in preventing bone loss and osteoporotic fractures in postmenopausal women, with no evidence of breast or endometrial stimulation. Two large, prospective, international phase 3 studies have been completed. In postmenopausal women at risk for osteoporosis, bazedoxifene has been shown to preserve bone mineral density and to reduce bone turnover. In postmenopausal women with osteoporosis, bazedoxifene has demonstrated significant protection against new vertebral fractures and against non-vertebral fractures in women at higher fracture risk. The treatment effects of bazedoxifene were supported by findings from independent re-analyses using the Fracture Risk Assessment Tool (FRAX), which showed that bazedoxifene significantly reduced the risk of all clinical and morphometric vertebral fracture and of non-vertebral fracture in women at or above a FRAX-based threshold. Bazedoxifene was generally safe and well tolerated in the phase 3 studies and showed neutral effects on the breast and an excellent endometrial safety profile; such attributes allow for the partnering of bazedoxifene with conjugated estrogens for menopausal symptom relief. Collectively, these results suggest that bazedoxifene may be a promising new therapy for the prevention and treatment of postmenopausal osteoporosis as a monotherapy or in combination with conjugated estrogens in menopausal hormone therapy.

Efficacy and safety of bazedoxifene, a novel selective estrogen receptor modulator for the prevention and treatment of postmenopausal osteoporosis

OBJECTIVE

Osteoporosis affects millions of individuals, particularly postmenopausal women, and imposes a severe burden on patients and the healthcare system. Several therapeutic options are commercially available for the prevention and treatment of osteoporosis, including bisphosphonates, hormone therapy, and the selective estrogen receptor modulator (SERM), raloxifene. Because each of these agents has its own individual risk-benefit profile, their use should be tailored to specific patient populations. While many agents are approved for osteoporosis, new therapies are needed that maximize efficacy outcomes and minimize safety concerns. Several new SERMs are being evaluated in an effort to achieve an ideal tissue selectivity profile, with beneficial effects on bone without negative effects on the endometrium and breast. Bazedoxifene is a novel SERM that was recently approved in the European Union and is undergoing regulatory review in the United States for the prevention and treatment of postmenopausal osteoporosis. This article reviews the clinical efficacy and safety data for bazedoxifene in postmenopausal women with or at risk for osteoporosis.

METHODS

The PubMed database and relevant congress abstract databases were searched to identify all pertinent literature on bazedoxifene for the prevention and/or treatment of postmenopausal osteoporosis.

RESULTS

In phase 3 clinical studies, bazedoxifene has demonstrated significant reduction in the risk of new vertebral fracture versus placebo and positive effects on bone mineral density and bone turnover. Moreover, in a subgroup analysis of women at high risk for fracture, bazedoxifene significantly reduced the risk of nonvertebral fracture versus both placebo and raloxifene. Bazedoxifene was generally safe and well-tolerated in women with and at risk for osteoporosis, with no evidence of endometrial or breast stimulation. Data inclusion for this review article was limited by what was available in the public domain.

CONCLUSION

The available clinical data suggest that bazedoxifene may offer a favorable risk-benefit profile for the prevention and treatment of postmenopausal osteoporosis.