Fulvestrant in the treatment of advanced breast cancer: A systematic review and meta-analysis of randomized controlled trials

Oral SERD, a Novel Endocrine Therapy for Estrogen Receptor-Positive Breast Cancer

Breast cancer is the most common cancer among women worldwide, and estrogen receptor-positive (ER+) breast cancer accounts for a significant proportion of cases. While various treatments are available, endocrine therapies are often the first-line treatment for this type of breast cancer. However, the development of drug resistance poses a significant challenge in managing this disease. ESR1 mutations have been identified as a common mechanism of endocrine therapy resistance in ER+ breast cancer. The first-generation selective estrogen receptor degrader (SERD) fulvestrant has shown some activity against ESR1 mutant tumors. However, due to its poor bioavailability and need for intramuscular injection, it may not be the optimal therapy for patients. Second-generation SERDs were developed to overcome these limitations. These newer drugs have improved oral bioavailability and pharmacokinetics, making them more convenient and effective for patients. Several oral SERDs are now in phase III trials for early and advanced ER+ breast cancer. This review summarizes the background of oral SERD development, the current status, and future perspectives.

Inhibition of Estrogen Signaling Reduces the Incidence of BRCA1-associated Mammary Tumor Formation

BRCA1-deficient breast cancer is a very well-known hereditary cancer. However, except for resection of normal mammary glands and ovaries, there is no acceptable measure for proactively preventing tumor development. Importantly, inherited BRCA1 mutations are closely associated with tumors in hormone-responsive tissues. Here, we examined the effects of estrogen on the accumulation of genetic instabilities upon loss of BRCA1, and assessed the contribution of estrogen signaling to the incidence and progression of Brca1-mutated mammary tumors. Our in vitro studies showed that treatment of BRCA1-depleted breast cancer cells with estrogen induced proliferation. Additionally, estrogen reduced the ability of these BRCA1-knockdown cells to sense radiation-induced DNA damage and also facilitated G1/S progression. Moreover, long-term treatment of Brca1-mutant (Brca1^co/coMMTV-Cre) mice with the selective estrogen receptor (ER)-α degrader, fulvestrant, decreased the tumor formation rate from 64% to 36%, and also significantly reduced mammary gland density in non-tumor-bearing mice. However, in vivo experiments showed that fulvestrant treatment did not alter the progression of ER-positive Brca1-mutant tumors, which were frequently identified in the aged population and showed less aggressive tendencies. These findings enhance our understanding of how ER-α signaling contributes to BRCA1-deficient mammary tumors and provide evidence suggesting that targeted inhibition of ER-α signaling may be useful for the prevention of BRCA1-mutated breast cancer.

Efficacy and safety of fulvestrant in postmenopausal patients with hormone receptor-positive advanced breast cancer: a systematic literature review and meta-analysis

PURPOSE

This meta-analysis was conducted to compare the efficacy and safety of fulvestrant with aromatase inhibitors in postmenopausal women with hormone receptor-positive (estrogen and/or progesterone receptor positive) advanced breast cancer.

METHODS

Electronic databases were searched for randomized controlled trials comparing the efficacy and safety of fulvestrant with three aromatase inhibitors (anastrozole/letrozole/exemestane) published through August 31, 2017. Time to progression/progression-free survival was the primary outcome, while overall survival and safety were the secondary outcomes. Time to progression/progression-free survival was evaluated in subgroups determined on age, hormone receptor status, visceral metastasis, and measurable disease. Hazard ratios with 95% confidence intervals were analyzed by STATA 12.0.

RESULTS

Total of seven randomized controlled trials, with 3168 patients were included for analysis. In the overall population, fulvestrant and aromatase inhibitors had similar time to progression/progression-free survival (Hazard ratio 0.93; 95% confidence interval 0.86-1.01, P = 0.102); however, time to progression/progression-free survival for fulvestrant 500 mg was significantly longer compared with aromatase inhibitors (hazard ratio 0.75; 95% confidence interval 0.62-0.91, P = 0.003). Subgroup analysis revealed significant prolongation of time to progression/progression-free survival with fulvestrant compared with aromatase inhibitors in the patients of estrogen and progesterone receptor-positive (hazard ratio 0.86; 95% confidence interval, 0.75-0.98, P = 0.022) and patients aged ≥ 65 years (hazard ratio 0.81; 95% confidence interval 0.68-0.96, P = 0.014). Overall survival was similar in both groups (hazard ratio 0.89; 95% confidence interval 0.70, 1.13, P = 0.334).

CONCLUSION

In postmenopausal women with estrogen and/or progesterone receptor-positive advanced breast cancer, fulvestrant 500 mg showed better efficacy than aromatase inhibitor, which was not seen with fulvestrant 250 mg. Compared to aromatase inhibitors, fulvestrant prolonged time to progression/progression-free survival in the subgroups including estrogen and progesterone receptor-positive patients and those aged ≥ 65 years.

The release of cardioprotective humoral factors after remote ischemic preconditioning in humans is age- and sex-dependent

Background

Preclinical and proof-of-concept studies suggest a cardioprotective effect of remote ischemic preconditioning (RIPC). However, two major clinical trials (ERICCA and RIPHeart) failed to show cardioprotection by RIPC. Aging and gender might be confounding factors of RIPC affecting the inter-organ signalling. Theoretically, confounding factors might prevent the protective potency of RIPC by interfering with cardiac signalling pathways, i.e. at the heart, and/or by affecting the release of humoral factor(s) from the remote organ, e.g. from the upper limb. This study investigated the effect of age and sex on the release of cardioprotective humoral factor(s) after RIPC in humans.

Methods

Blood samples were taken from young and aged, male and female volunteers before (control) and after RIPC (RIPC). To investigate the protective potency of the different plasma groups obtained from the human volunteers, isolated perfused hearts of young rats were used as bioassay. For this, hearts were perfused with the volunteer plasma (0.5% of coronary flow) before hearts underwent global ischemia and reperfusion. In addition, to characterize the protective potency of humoral factor(s) after RIPC to initiate protection not only in young but also aged hearts, plasma from young male volunteers were transferred to isolated hearts of aged rats. At the end of the experimental protocol, infarct sizes were determined by TTC-staining (expressed as % of left ventricle).

Results

RIPC plasma of young male volunteers reduced infarct size in young rat hearts from 47 ± 5 to 31 ± 10% (p = 0.02). In contrast, RIPC plasma of aged male volunteers had no protective effect. Infarct size after application of control plasma of young female volunteers was 33 ± 10%, and female RIPC plasma did not lead to an infarct size reduction. RIPC plasma of old female initiated no cardioprotection. RIPC plasma of young male volunteers reduced infarct size in isolated hearts from aged rats (41 ± 5% vs. 51 ± 5%; p < 0.001).

Conclusions

The release of humoral factor(s) into the blood after RIPC in humans is affected by both age and sex. In addition, these blood borne factor(s) are capable to initiate cardioprotection within the aged heart.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1480-0) contains supplementary material, which is available to authorized users.

Fulvestrant for hormone-sensitive metastatic breast cancer

BACKGROUND

Fulvestrant is a selective oestrogen receptor down-regulator (SERD), which by blocking proliferation of breast cancer cells, is an effective endocrine treatment for women with hormone-sensitive advanced breast cancer. The goal of such systemic therapy in this setting is to reduce symptoms, improve quality of life, and increase survival time.

OBJECTIVES

To assess the efficacy and safety of fulvestrant for hormone-sensitive locally advanced or metastatic breast cancer in postmenopausal women, as compared to other standard endocrine agents.

SEARCH METHODS

We searched the Cochrane Breast Cancer Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP), and ClinicalTrials.gov on 7 July 2015. We also searched major conference proceedings (American Society of Clinical Oncology (ASCO) and San Antonio Breast Cancer Symposium) and practice guidelines from major oncology groups (ASCO, European Society for Medical Oncology (ESMO), National Comprehensive Cancer Network, and Cancer Care Ontario). We handsearched reference lists from relevant studies.

SELECTION CRITERIA

We included for analyses randomised controlled trials that enrolled postmenopausal women with hormone-sensitive advanced breast cancer (TNM classifications: stages IIIA, IIIB, and IIIC) or metastatic breast cancer (TNM classification: stage IV) with an intervention group treated with fulvestrant with or without other standard anticancer therapy.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from trials identified in the searches, conducted 'Risk of bias' assessments of the included studies, and assessed the overall quality of the evidence using the GRADE approach. Outcome data extracted from these trials for our analyses and review included progression-free survival (PFS) or time to progression (TTP) or time to treatment failure, overall survival, clinical benefit rate, toxicity, and quality of life. We used the fixed-effect model for meta-analysis where possible.

MAIN RESULTS

We included nine studies randomising 4514 women for meta-analysis and review. Overall results for the primary endpoint of PFS indicated that women receiving fulvestrant did at least as well as the control groups (hazard ratio (HR) 0.95, 95% confidence interval (CI) 0.89 to 1.02; P = 0.18, I²= 56%, 4258 women, 9 studies, high-quality evidence). In the one high-quality study that tested fulvestrant at the currently approved and now standard dose of 500 mg against anastrozole, women treated with fulvestrant 500 mg did better than anastrozole, with a HR for TTP of 0.66 (95% CI 0.47 to 0.93; 205 women) and a HR for overall survival of 0.70 (95% CI 0.50 to 0.98; 205 women). There was no difference in PFS whether fulvestrant was used in combination with another endocrine therapy or in the first- or second-line setting, when compared to control treatments: for monotherapy HR 0.97 (95% CI 0.90 to 1.04) versus HR 0.87 (95% CI 0.77 to 0.99) for combination therapy when compared to control, and HR 0.93 (95% CI 0.84 to 1.03) in the first-line setting and HR 0.96 (95% CI 0.88 to 1.04) in the second-line setting.Overall, there was no difference between fulvestrant and control treatments in clinical benefit rate (risk ratio (RR) 1.03, 95% CI 0.97 to 1.10; P = 0.29, I² = 24%, 4105 women, 9 studies, high-quality evidence) or overall survival (HR 0.97, 95% CI 0.87 to 1.09, P = 0.62, I² = 66%, 2480 women, 5 studies, high-quality evidence). There was no significant difference in vasomotor toxicity (RR 1.02, 95% CI 0.89 to 1.18, 3544 women, 8 studies, high-quality evidence), arthralgia (RR 0.96, 95% CI 0.86 to 1.09, 3244 women, 7 studies, high-quality evidence), and gynaecological toxicities (RR 1.22, 95% CI 0.94 to 1.57, 2848 women, 6 studies, high-quality evidence). Four studies reported quality of life, none of which reported a difference between the fulvestrant and control arms, though specific data were not presented.

AUTHORS' CONCLUSIONS

For postmenopausal women with advanced hormone-sensitive breast cancer, fulvestrant is at least as effective and safe as the comparator endocrine therapies in the included studies. However, fulvestrant may be potentially more effective than current therapies when given at 500 mg, though this higher dosage was used in only one of the nine studies included in the review. We saw no advantage with combination therapy, and fulvestrant was equally as effective as control therapies in both the first- and second-line setting. Our review demonstrates that fulvestrant is a safe and effective systemic therapy and can be considered as a valid option in the sequence of treatments for postmenopausal women with hormone-sensitive advanced breast cancer.

Endocrine therapy resistance in estrogen receptor (ER)-positive breast cancer

Estrogen receptor (ER)-positive breast cancer represents the majority (∼70%) of all breast malignancies. In this subgroup of breast cancers, endocrine therapies are effective both in the adjuvant and recurrent settings, although resistance remains a major issue. Several high-throughput approaches have been used to elucidate mechanisms of resistance and to derive potential predictive markers or alternative therapies. In this review, we cover the state-of-the-art of endocrine-resistance biomarker discovery with regard to the latest technological developments, and discuss current opportunities and restrictions for their implementation into a clinical setting.

Endocrine Therapy for Hormone Receptor-Positive Metastatic Breast Cancer: American Society of Clinical Oncology Guideline

PURPOSE

To develop recommendations about endocrine therapy for women with hormone receptor (HR) -positive metastatic breast cancer (MBC).

METHODS

The American Society of Clinical Oncology convened an Expert Panel to conduct a systematic review of evidence from 2008 through 2015 to create recommendations informed by that evidence. Outcomes of interest included sequencing of hormonal agents, hormonal agents compared with chemotherapy, targeted biologic therapy, and treatment of premenopausal women. This guideline puts forth recommendations for endocrine therapy as treatment for women with HR-positive MBC.

RECOMMENDATIONS

Sequential hormone therapy is the preferential treatment for most women with HR-positive MBC. Except in cases of immediately life-threatening disease, hormone therapy, alone or in combination, should be used as initial treatment. Patients whose tumors express any level of hormone receptors should be offered hormone therapy. Treatment recommendations should be based on type of adjuvant treatment, disease-free interval, and organ function. Tumor markers should not be the sole criteria for determining tumor progression; use of additional biomarkers remains experimental. Assessment of menopausal status is critical; ovarian suppression or ablation should be included in premenopausal women. For postmenopausal women, aromatase inhibitors (AIs) are the preferred first-line endocrine therapy, with or without the cyclin-dependent kinase inhibitor palbociclib. As second-line therapy, fulvestrant should be administered at 500 mg with a loading schedule and may be administered with palbociclib. The mammalian target of rapamycin inhibitor everolimus may be administered with exemestane to postmenopausal women with MBC whose disease progresses while receiving nonsteroidal AIs. Among patients with HR-positive, human epidermal growth factor receptor 2-positive MBC, human epidermal growth factor receptor 2-targeted therapy plus an AI can be effective for those who are not chemotherapy candidates.

SRC drives growth of antiestrogen resistant breast cancer cell lines and is a marker for reduced benefit of tamoxifen treatment

The underlying mechanisms leading to antiestrogen resistance in estrogen-receptor α (ER)-positive breast cancer is still poorly understood. The aim of this study was therefore to identify biomarkers and novel treatments for antiestrogen resistant breast cancer. We performed a kinase inhibitor screen on antiestrogen responsive T47D breast cancer cells and T47D-derived tamoxifen and fulvestrant resistant cell lines. We found that dasatinib, a broad-spectrum kinase inhibitor, inhibited growth of the antiestrogen resistant cells compared to parental T47D cells. Furthermore western blot analysis showed increased expression and phosphorylation of Src in the resistant cells and that dasatinib inhibited phosphorylation of Src and also signaling via Akt and Erk in all cell lines. Immunoprecipitation revealed Src: ER complexes only in the parental T47D cells. In fulvestrant resistant cells, Src formed complexes with the Human Epidermal growth factor Receptor (HER)1 and HER2. Neither HER receptors nor ER were co-precipitated with Src in the tamoxifen resistant cell lines. Compared to treatment with dasatinib alone, combined treatment with dasatinib and fulvestrant had a stronger inhibitory effect on tamoxifen resistant cell growth, whereas dasatinib in combination with tamoxifen had no additive inhibitory effect on fulvestrant resistant growth. When performing immunohistochemical staining on 268 primary tumors from breast cancer patients who had received tamoxifen as first line endocrine treatment, we found that membrane expression of Src in the tumor cells was significant associated with reduced disease-free and overall survival. In conclusion, Src was identified as target for treatment of antiestrogen resistant T47D breast cancer cells. For tamoxifen resistant T47D cells, combined treatment with dasatinib and fulvestrant was superior to treatment with dasatinib alone. Src located at the membrane has potential as a new biomarker for reduced benefit of tamoxifen.

Goserelin plus endocrine treatments maintained long-term clinical benefit in a male patient with advanced breast cancer

Background

Goserelin plus aromatase inhibitors (AI) have already been used in male advanced breast cancer, but the cases that fulvestrantin male breast cancer are rare.

Case presentation

Here we report a case of long-term (3 years) response to Goserelin plus continuing endocrine treatments given for a male advanced breast cancer. The patient prolongs his life with high life quality, and has more time with his family.

Conclusion

Goserelin plus endocrine treatments may benefit male breast cancer.

Fulvestrant 250 mg versus anastrozole 1 mg in the treatment of advanced breast cancer: a meta-analysis of randomized controlled trials

OBJECTIVE

Most patients with advanced breast cancer experience resistance to endocrine treatment and eventual disease progression. This meta-analysis was designed to compare the efficacy and tolerability of fulvestrant 250 mg with anastrozole 1mg in postmenopausal women with advanced breast cancer.

METHODS

Electronic literature databases (Cochrane Library, Medline, and Embase) were searched for randomized controlled trials (RCTs) published prior to August 2013. Only RCTs that compared fulvestrant 250 mg to anastrozole 1mg in postmenopausal women with advanced breast cancer were selected. The main outcomes were time to treatment failure (TTF), time to progression (TTP), duration of response (DOR), clinical benefit rate, and tolerability.

RESULTS

Four RCTs covering 1,226 patients (fulvestrant, n=621; anastrozole, n=605) were included in the meta-analysis. Fulvestrant increased the DOR compared to anastrozole (HR =1.31, 95% confidence interval [CI] 1.13-1.51). There was no statistically significant difference between fulvestrant and anastrozole in terms of TTF (HR=1.02, 95%CI 0.89-1.17), complete response (RR=1.79, 95%CI, 0.93-3.43), and partial response (RR=0.91, 95%CI 0.69-1.21). As for safety, there was no statistical significance between the two groups for common adverse events.

CONCLUSION

Fulvestrant 250 mg is as effective and well-tolerated as anastrozole 1mg treatment for advanced breast cancer in postmenopausal women whose disease progressed after prior endocrine treatment. Thus, fulvestrant may serve as a reasonable alternative to anastrozole when resistance is experienced in breast cancer cases.

The broad-spectrum metalloproteinase inhibitor BB-94 inhibits growth, HER3 and Erk activation in fulvestrant-resistant breast cancer cell lines

Breast cancer cells can switch from estrogen receptor α (ER)- to human epidermal growth factor receptor (HER)-driven cell growth upon acquiring antiestrogen resistance. HER ligands are cleaved by metalloproteinases leading to release of active HER ligands, activation of HER receptors and consequently increased cell growth. In this study, we investigated the importance of HER receptors, in particular HER3, and HER ligand shedding for growth and signaling in human MCF-7 breast cancer cells and MCF-7-derived sublines resistant to the antiestrogen fulvestrant. The HER3/HER4 ligand heregulin 1β induced phosphorylation of HER3, Akt and Erk, and partly rescued fulvestrant-inhibited growth of MCF-7 cells. HER3 ligands were found to be produced and shed from the fulvestrant-resistant cells as conditioned medium from fulvestrant-resistant MCF-7 cells induced phosphorylation of HER3 and Akt in MCF-7 cells. This was prevented by treatment of resistant cells with the metalloproteinase inhibitor TAPI-2. Only the broad-spectrum metalloproteinase inhibitor BB-94, and not the more selective inhibitors GM6001 or TAPI-2, which inhibited shedding of the HER ligands produced by the fulvestrant-resistant cells, was able to inhibit growth and activation of HER3 and Erk in resistant cells. Compared to MCF-7, fulvestrant-resistant cells have increased HER3 phosphorylation, but knockdown of HER3 had no inhibitory effect on resistant cell growth. The EGFR inhibitor gefitinib exhibited only a minor growth inhibition, whereas the pan-HER inhibitor CI-1033 exerted growth arrest. Thus, neither HER3 nor EGFR alone are the main driver of fulvestrant-resistant cell growth and treatment should target both receptors. Ligand shedding is not a treatment target, as receptor activation occurred, independent of release of ligands. Only the broad-spectrum metalloproteinase inhibitor BB-94 could abrogate HER3 and Erk activation in the resistant cells, which stresses the complexity of the resistance mechanisms and the requirement of targeting signaling from HER receptors by multiple strategies.

N0539 phase II trial of fulvestrant and bevacizumab in patients with metastatic breast cancer previously treated with an aromatase inhibitor: a North Central Cancer Treatment Group (now Alliance) trial

BACKGROUND

Based on preclinical studies, the vascular endothelial pathway is an important mechanism for estrogen receptor resistance. We conducted a phase II study of fulvestrant and bevacizumab in patients with aromatase inhibitor pretreated metastatic breast cancer.

PATIENTS AND METHODS

A single-stage phase II study was conducted with these objectives: 6-month progression-free survival (PFS), tumor response, toxic effect, and overall survival. Regimen: 250 mg fulvestrant days 1 and 15 (cycle 1) then day 1 (cycle 2 and beyond) and 10 mg/kg bevacizumab days 1 and 15 of each 4-week cycle.

RESULTS

At interim analysis, 20 eligible patients initiated treatment, 11 were progression free and on treatment at 3 months, not meeting the protocol-specified efficacy requirements (at least 12 of 20). Accrual remained open during interim analysis with 36 patients enrolling before final study closure. Among the 33 eligible patients, the median PFS was 6.2 months [95% confidence interval (CI) 3.6-10.1 months]. Of the 18 with measurable disease, 4 (22%) patients (95% CI 6% to 48%) had a confirmed tumor response (1 complete, 3 partial). The most common grade 3/4 adverse events were hypertension 3 (9%) and headache 3 (9%).

CONCLUSIONS

The fulvestrant/bevacizumab combination is safe and tolerable; however, it did not meet its statistical end point.

Tissue selective estrogen complexes (TSECs) differentially modulate markers of proliferation and differentiation in endometrial cells

Selective estrogen receptor modulators (SERMs) have tissue-specific estrogen receptor (ER) modulating properties. Combining an SERM with one or more estrogens to form a tissue selective estrogen complex (TSEC) can provide an improved blend of tissue-specific ER agonist and antagonist effects. While both estrogens and SERMs affect the uterine endometrium, not all TSECs reverse the endometrial effects of estrogens preventing endometrial proliferation and hyperplasia. Their action in uterine cells is not completely understood. HOXA 10, leukemia inhibitory factor (LIF), progesterone receptor (PR), and EMX2 are genes known to regulate endometrial proliferation and differentiation. The expression of these genes was used to assess endometrial effects of SERMs and TSECs. We evaluated the effects of raloxifene (RAL), tamoxifen (TAM), lasofoxifene (LAS), bazedoxifene acetate (BZA), and progesterone (P) alone and in combination with estradiol (E2) in Ishikawa cells. Increased HOXA10, LIF, PR, and EMX2 messenger RNA (mRNA) expression was noted in E2-treated cells compared with vehicle-treated controls. All TSECs maintained E2-induced PR expression and all except TAM prevented estrogen-induced LIF expression. The TSEC containing BZA uniquely decreased HOXA10 expression and increased EMX2 expression. The TSECs alter endometrial cell proliferation by selective modulation of estrogen responsive genes, maintaining the antiproliferative effects mediated by PR and inhibiting LIF. The differential effect of TSECs on endometrial gene expression suggests a mechanism by which they manifest differential effects on endometrial safety against the risk of estrogen-induced endometrial hyperplasia.

Combining Src inhibitors and aromatase inhibitors: a novel strategy for overcoming endocrine resistance and bone loss

Aromatase inhibitors have largely replaced tamoxifen as the first-line treatment for postmenopausal women with metastatic, hormone receptor-positive (HR+) breast cancer. However, many patients develop clinical resistance with prolonged treatment, and oestrogen deprivation following aromatase inhibition can result in loss of bone mineral density. Furthermore, most patients with metastatic breast cancer develop bone metastases, and the resulting adverse skeletal-related events are a significant cause of patient morbidity. Src, a non-receptor tyrosine kinase, is a component of signalling pathways that regulate breast cancer cell proliferation, invasion and metastasis as well as osteoclast-mediated bone turnover. Preclinical evidence also suggests a role for Src in acquired endocrine resistance. As such, Src inhibition represents a logical strategy for the treatment of metastatic breast cancer. In vitro, combination therapy with Src inhibitors and endocrine agents, including aromatase inhibitors, has been shown to inhibit the proliferation and metastasis of both endocrine-responsive and endocrine-resistant breast cancer cell lines more effectively than either of the therapy alone. Src inhibition has also been shown to suppress osteoclast formation and activity. Combination therapy with aromatase inhibitors and Src inhibitors therefore represents a novel approach through which the development of both acquired resistance and bone pathology could be delayed. Data from clinical trials utilising such combinations will reveal if this strategy has the potential to improve patient outcomes.