A randomized trial of combination anastrozole plus gefitinib and of combination fulvestrant plus gefitinib in the treatment of postmenopausal women with hormone receptor positive metastatic breast cancer. Breast Cancer Res Treat. 2012;133:1049-1056. [PMID: 22418699 DOI: 10.1007/s10549-012-1997-5]

X-ray crystallography study and optimization of novel benzothiophene analogs as potent selective estrogen receptor covalent antagonists (SERCAs) with improved potency and safety profiles

Endocrine therapy (ET) is a well-validated strategy for estrogen receptor α positive (ERα + ) breast cancer therapy. Despite the clinical success of current standard of care (SoC), endocrine-resistance inevitably emerges and remains a significant medical challenge. Herein, we describe the structural optimization and evaluation of a new series of selective estrogen receptor covalent antagonists (SERCAs) based on benzothiophene scaffold. Among them, compounds 15b and 39d were identified as two highly potent covalent antagonists, which exhibits superior antiproliferation activity than positive controls against MCF-7 cells and shows high selectivity over ERα negative (ERα-) cells. More importantly, their mode of covalent engagement at Cys530 residue was accurately illustrated by a cocrystal structure of 15b-bound ERαY537S (PDB ID: 7WNV) and intact mass spectrometry, respectively. Further in vivo studies demonstrated potent antitumor activity in MCF-7 xenograft mouse model and an improved safety profile. Collectively, these compounds could be promising candidates for future development of the next generation SERCAs for endocrine-resistant ERα + breast cancer.

Tyrosine kinase inhibitors in breast cancer (Review)

Anti-epidermal growth factor receptor (EGFR)-targeted therapy has been intensely researched in the last years, motivated by the favorable results obtained with monoclonal antibodies in HER2-enriched breast cancer (BC) patients. Most researched alternatives of anti-EGFR agents were tyrosine kinase inhibitors (TKIs) and monoclonal antibodies. However, excluding monoclonal antibodies trastuzumab and pertuzumab, the remaining anti-EGFR molecules have exhibited disappointing results, due to the lack of specificity and frequent adverse side effects. TKIs have several advantages, including reduced cardiotoxicity, oral administration and favorable penetration of blood-brain barrier for brain metastatic BC. Lapatinib and neratinib and recently pyrotinib (approved only in China) are the only TKIs from dozens of molecules researched over the years that were approved to be used in clinical practice with limited indications, in a subset of BC patients, single or in combination with other chemotherapy or hormonal therapeutic agents. Improved identification of BC subtypes and improved characterization of aggressive forms (triple negative BC or inflammatory BC) should lead to advancements in shaping of targeted agents to improve the outcome of patients.

Multikinase inhibitor-induced liver injury in patients with cancer: A review for clinicians

BACKGROUND

Multikinase inhibitors (MKI) are targeted molecular agents that have revolutionized cancer management. However, there is a paucity of data concerning MKI-related liver injury risk and clinical guidelines for the management of liver toxicity in patients receiving MKI for cancer are scarce.

DESIGN

We conducted a PubMed search of articles in English published from January 2000 to December 2018 related to hepatotoxicity of the 29 FDA-approved MKIs at doses used in clinical practice. The search terms were the international non-proprietary name of each agent cross-referenced with «hepatotoxicity», «hepatitis», «hepatic adverse event», or «liver failure», and «phase II clinical trial», «phase III clinical trial», or «case report».

RESULTS

Following this search, 140 relevant studies and 99 case reports were considered. Although asymptomatic elevation of aminotransferase levels has been frequently observed in MKI clinical trials, clinically significant hepatotoxicity is a rare event. In most cases, the interval between treatment initiation and the onset of liver injury is between one week and two months. Liver toxicity is often hepatocellular and less frequently mixed. Life-threatening MKI-induced hepatic injury has been described, involving fulminant liver failure or death. Starting from existing data, a description of MKI-related liver events, grading of hepatotoxicity risk, and recommendations for management are also given for various MKI molecules.

CONCLUSION

All MKIs can potentially cause liver injury, which is sometimes irreversible. As there is still no strategy available to prevent MKI-related hepatotoxicity, early detection remains crucial. The surveillance of liver function during treatment may help in the early detection of hepatotoxicity. Furthermore, the exclusion of potential causes of hepatic injury is essential to avoid unnecessary MKI withdrawal.

Review of concepts in therapeutic decision-making in HER2-negative luminal metastatic breast cancer

Purpose

Hormone receptor (HR)-positive, Human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC) requires a therapeutic approach that takes into account multiple factors, with treatment being based on anti-estrogen hormone therapy (HT). As consensus documents are valuable tools that assist in the decision-making process for establishing clinical strategies and optimize the delivery of health services, this consensus document has been created with the aim of developing recommendations on cretiera for hormone sensitivity and resistance in HER2-negative luminal MBC and facilitating clinical decision-making.

Methods

This consensus document was generated using a modification of the RAND/UCLA methodology, which included the definition of the project and identification of issues of interest, a non-exhaustive systematic review of the literature, an analysis and synthesis of the scientific evidence, preparation of recommendations, and external evaluation with a panel of 64 medical oncologists specializing in breast cancer.

Results

A Spanish panel of experts reached consensus on 32 of the 32 recommendations/conclusions presented in the first round and were accepted with an approval rate of 100% about definition of metastatic disease not susceptible to local curative treatment, definition of hormone sensitivity and hormone resistance in metastatic luminal disease and therapeutic decision-making.

Conclusion

We have developed a consensus document with recommendations on the treatment of patients with HER2-negative luminal MBC that will help to improve therapeutic benefits.

CDK4/6 inhibition versus mTOR blockade as second-line strategy in postmenopausal patients with hormone receptor-positive advanced breast cancer: A network meta-analysis

BACKGROUND

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors (palbociclib and abemaciclib) and mammalian target of rapamycin (mTOR) inhibitors (everolimus) are effective agents for restoring endocrine sensitivity in patients with advanced breast cancer progression on prior aromatase inhibitors. We conducted a network meta-analysis to compare these treatments in terms of progression-free survival (PFS), objective response rate (ORR), and clinical benefit rate (CBR).

METHODS

The PubMed and Embase databases were searched for relevant publications between January 2000 and June 2018. Treatments were ranked based on a network meta-analysis. Ranking was determined by P-score. A random-effect model was used when heterogeneity was detected; otherwise, a fixed-effect model was used.

RESULTS

Six trials comprising 4063 patients formed the comparison network. Compared with everolimus plus exemestane, the combinations of palbociclib or abemaciclib with fulvestrant showed similar efficacies in PFS and no differences in ORR. For the CBR, palbociclib demonstrated improvement, while abemaciclib did not. Incidences of severe adverse events did not significantly differ. A total of 29%, 15.9%, and 4% of patients discontinued everolimus, abemaciclib, and palbociclib, respectively, due to toxicity.

CONCLUSION

These results suggest similar efficacies between CDK4/6 inhibition and mTOR blockade; however, CDK4/6 inhibitors were associated with favorable toxicity profiles.

Signaling pathways and steroid receptors modulating estrogen receptor α function in breast cancer

Estrogen receptor α (ER) is the major driver of ∼75% of breast cancers, and multiple ER targeting drugs are routinely used clinically to treat patients with ER+ breast cancer. However, many patients relapse on these targeted therapies and ultimately develop metastatic and incurable disease, and understanding the mechanisms leading to drug resistance is consequently of utmost importance. It is now clear that, in addition to estrogens, ER function is modulated by other steroid receptors and multiple signaling pathways (e.g., growth factor and cytokine signaling), and many of these pathways affect drug resistance and patient outcome. Here, we review the mechanisms through which these pathways impact ER function and drug resistance as well as discuss the clinical implications.

Clinical utility of fulvestrant in the treatment of breast cancer: a report on the emerging clinical evidence

Fulvestrant is the first selective estrogen receptor (ER) downregulator available in clinical practice. It is a pure antiestrogen with no agonistic effects, leading to degradation of ER alpha, with activity in tamoxifen-resistant breast cancer (BC) models. Pharmacokinetic and pharmacodynamic studies and several postmarketing clinical trials led to the definition of the optimal dose at 500 mg intramuscularly on days 1, 15, and 29 and then every 28 days. Targeting ER alpha, fulvestrant is a cornerstone of treatment in luminal BCs, whose growth is largely driven by the ER pathway. In endocrine therapy-naïve patients with hormone receptor-positive, HER2− advanced BC (ABC), fulvestrant yielded significantly longer progression-free survival compared to anastrozole in the Phase III FALCON study. Due to its mechanism of action and pharmacokinetic properties, fulvestrant is an ideal backbone for combination therapies. Preclinical studies have shown synergism with drugs acting on signaling pathways involved in the development of endocrine resistance, among which the cyclin D/cyclin-dependent kinase 4-6/retinoblastoma pathway and the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin pathway, contributing to overcoming or delaying endocrine resistance. In the Phase III PALOMA-3 trial, a combination of the cyclin-dependent kinase 4/6 inhibitor palbociclib with fulvestrant significantly improved progression-free survival over fulvestrant alone in women with hormone receptor positive, HER2− ABC progressing during prior endocrine therapy. This led to approval of the combination in this clinical setting. Similar results were obtained with abemaciclib and ribociclib. Combination with pan-PI3K inhibitors, though showing some efficacy, was hampered by the toxicity of these agents, and studies in combinations with more selective inhibitors of the α-catalytic subunit of PI3K are ongoing. Fulvestrant has shown partial activity also in patients with tumors harboring mutations of the ESR1 gene. It is thus a key drug in the treatment of ABC, whose role in combination with new targeted agents is still evolving.

Optimising endocrine therapy in postmenopausal women with advanced breast cancer

Hormone receptor-positive breast cancer is commonly treated with endocrine therapy (ET); however, over time, cancer cells can develop endocrine resistance. This review aims to document combination therapy and sequential therapy in the use of endocrine agents and targeted agents, by conducting two systematic searches using four databases: Cochrane Library, MEDLINE, EMBASE and Web of Science. A total of 26 studies that covered combination therapy were obtained and included for the review. Fourteen were phase III documenting combinations of mechanistic target of rapamycin (mTOR), phosphoinositide-3-kinase (PI3K), vascular endothelial growth factor receptor, human epidermal growth factor receptor 2 and cyclin-dependent kinase 4/6 (CDK4/6) inhibitors. The remaining studies were of phase II nature that reported combinations involving inhibitors in mTOR, endothelial growth factor receptor, CDK4/6 and TKI. Interesting findings in inhibitor combinations involving CDK4/6, mTOR and PI3K suggest clinical activity that can overcome endocrine resistance. On the other hand, there were 0 studies that covered sequential therapy. Overall findings showed that combination therapy improved treatment efficacy over monotherapy in postmenopausal patients with hormone receptor-positive advanced breast cancer. Inevitably, the benefits are accompanied with increased toxicity. To optimise ET, further research into combinations and effective patient selection will need to be defined. Additionally, this review warrants future studies to explore sequential therapy.

Treatment for the endocrine resistant breast cancer: Current options and future perspectives

Endocrine resistance remains a challenge and an unmet need for managing hormone receptor-positive breast cancer. The mechanisms of endocrine resistance are multifaceted and are likely to evolve over time following various single or combination therapies. The purpose of this review article is to provide general understanding of molecular basis of endocrine resistance of breast cancer and to offer comprehensive review on current treatment options and potential new treatment strategies for endocrine resistant breast cancers. Last but not the least, we discuss current challenges and future directions for management of endocrine resistant breast cancers.

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.

Treatment with aromatase inhibitors stimulates the expression of epidermal growth factor receptor-1 and neuregulin 1 in ER positive/HER-2/neu non-amplified primary breast cancers

While estrogens have been shown to modulate EGFR/HER-1 and HER-2/neu expression in experimental systems, the effects of estrogen deprivation on expression levels of the HER-receptors and the neuregulin (NRG)1 ligand in breast cancers remain unknown. Here, we measured EGFR/HER-1-4 and NRG1 mRNA in ER positive tumors from 85 postmenopausal breast cancer patients before and after two weeks (n=64) and three months (n=85) of primary treatment with an aromatase inhibitor (AI). In tumors lacking HER-2/neu amplification, quantitative real-time PCR analyses revealed EGFR/HER-1 and NRG1 to vary significantly between the three time points (before therapy, after 2 weeks and after 3 months on treatment; P≤0.001 for both). Pair-wise comparison revealed a significant increase in EGFR/HER-1 already during the first two weeks of treatment (P=0.049) with a further increase for both EGFR/HER-1 and NRG1 after 3 months on treatment (P≤0.001 and P=0.001 for both comparing values at 3 months to values at baseline and 2 weeks respectively). No difference between tumors responding versus non-responders was recorded. Further, no significant change in any parameter was observed among HER-2/neu amplified tumors. Analyzing components of the HER-2/neu PI3K/Akt downstream pathway, the PIK3CA H1047R mutation was associated with treatment response (P=0.035); however no association between either AKT phosphorylation status or PIK3CA gene mutations and EGFR/HER-1 or NRG1 expression levels were observed. Our results indicate primary AI treatment to modulate expression of HER-family members and the growth factor NRG1 in HER-2/neu non-amplified breast cancers in vivo. Potential implications to long term sensitivity warrants further investigations.

Accurate prediction of response to endocrine therapy in breast cancer patients: current and future biomarkers

Approximately 70% of patients have breast cancers that are oestrogen receptor alpha positive (ER+) and are therefore candidates for endocrine treatment. Many of these patients relapse in the years during or following completion of adjuvant endocrine therapy. Thus, many ER+ cancers have primary resistance or develop resistance to endocrine therapy during treatment. Recent improvements in our understanding of how tumours evolve during treatment with endocrine agents have identified both changes in gene expression and mutational profiles, in the primary cancer as well as in circulating tumour cells. Analysing these changes has the potential to improve the prediction of which specific patients will respond to endocrine treatment. Serially profiled biopsies during treatment in the neoadjuvant setting offer promise for accurate and early prediction of response to both current and novel drugs and allow investigation of mechanisms of resistance. In addition, recent advances in monitoring tumour evolution through non-invasive (liquid) sampling of circulating tumour cells and cell-free tumour DNA may provide a method to detect resistant clones and allow implementation of personalized treatments for metastatic breast cancer patients. This review summarises current and future biomarkers and signatures for predicting response to endocrine treatment, and discusses the potential for using approved drugs and novel agents to improve outcomes. Increased prediction accuracy is likely to require sequential sampling, utilising preoperative or neoadjuvant treatment and/or liquid biopsies and an improved understanding of both the dynamics and heterogeneity of breast cancer.

Hormone receptor positive, HER2 negative metastatic breast cancer: A systematic review of the current treatment landscape

Endocrine therapy for the treatment of hormone receptor positive, HER2 negative, metastatic breast cancer is continually evolving. We systematically reviewed phase 2 and 3 randomized controlled trials (RCTs) of agents used in this setting to assess the effectiveness and safety of these agents for postmenopausal women. Across the 32 studies in more than 10,000 patients, the greatest improvement in progression-free survival (PFS) was seen with the addition of a cyclin-dependent kinase (CDK)4/6 inhibitor to standard endocrine therapy. Treatment with a mammalian target of rapamycin (mTOR) inhibitor, phosphoinositol-3-kinase (Pi3K) inhibitor, vascular endothelial growth factor (VEGF) inhibitor and with a selective estrogen receptor degrader (SERD) also showed benefit in PFS for selected trials. Overall survival (OS) improved with the use of mTOR inhibitors and a SERD; however, studies were not powered for an OS endpoint. Encouraging results from early studies of histone deacetylase (HDAC) and B-cell lymphoma (BCL2) inhibitors are yet to be confirmed in phase III clinical trials. Study discontinuation rates and toxicity-related deaths were highest with VEGF inhibitors in combination with endocrine therapy, limiting their use in hormone receptor positive breast cancer. CDK4/6 inhibitors and mTOR inhibitors appeared to have activity in both first and second line settings, but required additional monitoring for common toxicities. The activity of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors was limited to the first-line setting and treatment discontinuation rates were higher than with mTOR inhibitors and SERDs. Overall, PFS benefit appears to be greatest when agents acting on CDK4/6, mTOR and Pi3K pathways, and SERDs are added to standard endocrine therapy. If these early results persist in further studies, these data are likely to change the way we treat hormone receptor positive, HER2 negative metastatic breast cancer. In the follow-up article to this review, we will consider the potential future treatment options for these patients.

New and developing chemical pharmacotherapy for treating hormone receptor-positive/HER2-negative breast cancer

INTRODUCTION

Endocrine therapy is the mainstay of treatment for a substantial proportion of hormone receptor positive (HR+) breast cancer (BC). Indeed, patients with metastatic disease not immediately life threatening may experience long disease control across several lines of endocrine therapy. The major limitation of this therapeutic approach is primary or acquired resistance. A better understanding of endocrine resistance has resulted in newer targeted agents to be added to endocrine therapy. Areas covered: This review highlights new findings in the treatment of HR+/HER2- BC, with a particular focus on new drugs from phase 3 development onwards. Expert opinion: Combining endocrine therapy with agents targeting putative mechanisms of endocrine resistance is a newer treatment paradigm in HR+ BC. Adding a biologically targeted agent to endocrine therapy results in improved response rate, and clinical benefit rate, and prolonged progression-free survival. A clear advantage in overall survival has not yet been reported. Combination therapy allows to delay chemotherapy but increases toxicities and costs, which are critical factors in decision making in the clinical practice. Moreover, identification and validation of biomarkers of response are needed. Ongoing and future trials should elucidate the role of these compounds in the treatment of HR+/HER2- BC.

Endocrine therapy and strategies to overcome therapeutic resistance in breast cancer

Despite the remarkable success of endocrine therapy in the treatment of patients with estrogen receptor (ER)- positive breast cancer, not all patients derive benefit from such therapy, or may benefit only temporarily before disease progression or relapse occurs. The value of endocrine therapy, which blocks ER signaling by a variety of strategies, lies in its simplicity, lower toxicity, and better alignment with preserved quality of life, particularly when compared to chemotherapy, which is more toxic and has only modest benefits for many patients with ER-positive breast cancer. It is therefore critical that we discover ways to extend endocrine therapy benefit in patients and prevent therapeutic resistance whenever possible. The tremendous evolution in our understanding of endocrine resistance mechanisms, coupled with the increasing availability of novel agents that target resistance pathways, has led to enhanced treatment approaches for patients with ER-positive breast cancer, primarily through combinations of endocrine agents with a variety of pathway inhibitors. Despite these treatment advances and our changing view of ER-positive breast cancer, there is much work that needs to be done. It remains a problem that we cannot reliably predict which subsets of patients will experience disease relapse or progression on endocrine therapy, and as such, combination strategies with targeted agents have largely been used in unselected patients with ER-positive breast cancer, including those who continue to have endocrine-sensitive disease. Patient selection is a significant issue since most of the targeted therapeutics that we use with endocrine therapy are expensive and can be toxic, and we may be inadvertently overtreating patients whose disease can still be controlled with endocrine therapy alone. In this article, we will review current and future strategies in the treatment of ER-positive breast cancer, as well as the evolving role of targeted therapy in the management of endocrine-resistance.

Review of hormone-based treatments in postmenopausal patients with advanced breast cancer focusing on aromatase inhibitors and fulvestrant

Background

Endocrine therapy constitutes a central modality in the treatment of oestrogen receptor (ER)-positive advanced breast cancer.

Purpose

To evaluate the evidence for endocrine treatment in postmenopausal patients with advanced breast cancer focusing on the aromatase inhibitors, letrozole, anastrozole, exemestane and fulvestrant.

Methods

A review was carried out using PubMed. Randomised phase II and III trials reporting on ≥100 patients were included.

Results

35 trials met the inclusion criteria. If not used in the adjuvant setting, a non-steroid aromatase inhibitor was the optimal first-line option. In general, the efficacy of the different aromatase inhibitors and fulvestrant was similar in tamoxifen-refractory patients. A randomised phase II trial of palbociclib plus letrozole versus letrozole alone showed significantly increased progression-free survival (PFS) when compared with endocrine therapy alone in the first-line setting (20.2 vs 10.2 months). Furthermore, the addition of everolimus to exemestane in the Breast Cancer Trials of OraL EveROlimus-2 (BOLERO-2) study resulted in an extension of median PFS by 4.5 months after recurrence/progression on a non-steroid aromatase inhibitor. However, overall survival was not significantly increased.

Conclusion

Conventional treatment with an aromatase inhibitor or fulvestrant may be an adequate treatment option for most patients with hormone receptor-positive advanced breast cancer. Mammalian target of rapamycin (mTOR) inhibition and cyclin-dependent kinase 4/6 (CDK4/6) inhibition might represent substantial advances for selected patients in some specific settings. However, there is an urgent need for prospective biomarker-driven trials to identify patients for whom these treatments are cost-effective.

Treatment challenges for community oncologists treating postmenopausal women with endocrine-resistant, hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer

Community-based oncologists are faced with challenges and opportunities when delivering quality patient care, including high patient volumes and diminished resources; however, there may be the potential to deliver increased patient education and subsequently improve outcomes. This review discusses the treatment of postmenopausal women with endocrine-resistant, hormone receptor-positive, human epidermal growth factor receptor 2- negative advanced breast cancer in order to illustrate considerations in the provision of pertinent quality education in the treatment of these patients and the management of therapy-related adverse events. An overview of endocrine-resistant breast cancer and subsequent treatment challenges is also provided. Approved treatment options for endocrine-resistant breast cancer include hormonal therapies and mammalian target of rapamycin inhibitors. Compounds under clinical investigation are also discussed.

Delaying Chemotherapy in the Treatment of Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer

Global guidelines for the management of locally advanced or metastatic hormone receptor-positive (HR-positive), human epidermal growth factor 2-negative (HER2-negative) breast cancer recommend endocrine therapy as first-line treatment for all patients, regardless of age or postmenopausal status. However, current practice patterns in the United States and Europe suggest that these modes of therapy are not being used as recommended, and many patients with advanced HR-positive, HER2-negative disease are being treated first-line with chemotherapy or switched to chemotherapy after a single endocrine therapy. Given that chemotherapy is associated with increased toxicity and reduced quality of life (QOL) compared with endocrine therapy, prolonging the duration of response obtained with endocrine therapy may help delay chemotherapy and its attendant toxicities. Several strategies to delay or overcome endocrine resistance and thereby postpone chemotherapy have been explored, including the use of second-line endocrine agents with different mechanisms of action, adding targeted agents that inhibit specific resistance pathways, and adding agents that act in complementary or synergistic ways to inhibit tumor cell proliferation. This review analyzes the different therapy options available to HR-positive, HER2-negative patients with advanced breast cancer that can be used to delay chemotherapy and enhance QOL.

A European Organisation for Research and Treatment of Cancer randomized, double-blind, placebo-controlled, multicentre phase II trial of anastrozole in combination with gefitinib or placebo in hormone receptor-positive advanced breast cancer (NCT00066378)

BACKGROUND

Preclinical data suggest that epidermal growth factor receptor (EGFR) inhibitors (e.g. gefitinib) can delay endocrine resistance in breast cancer. A double-blind, placebo-controlled, phase II trial investigated whether adding gefitinib (G) to anastrozole (A) would improve outcome in advanced breast cancer (ABC).

METHODS

Postmenopausal pre-treated hormone receptor-positive ABC patients (locally recurrent or metastatic) were 1:1 randomized to A (1 mg/d) plus G 250 mg/d or plus placebo (P). Patients who had prior treatment with an aromatase inhibitor in metastatic setting or with trastuzumab, anti-EGFR or anti-VEGF agents were excluded. Treatment was given until disease progression, unacceptable toxicity or patient withdrawal. Progression-free survival (PFS) rate at 1 year was assessed according to Response Evaluation Criteria in Solid Tumours, version 1.0.

RESULTS

Of 108 planned patients, 71 were recruited (36 in A/G and 35 in A/P). The trial closed prematurely due to slow recruitment; 31 patients had prior chemotherapy and 53 prior endocrine therapy (all except one received tamoxifen); 60% in adjuvant and 16% in metastatic setting received tamoxifen; 59 patients had visceral disease. Median follow-up was 18 months. PFS rate at 1 year was 35% for A/G and 32% for A/P arm. Objective responses were six (22%) in the A/G and nine (28%) in the A/P arm. Median duration of response was 13.8 and 18.6 months in the A/G and A/P arms, respectively. Fatigue (35%), diarrhoea (31%), rash (32%), dry skin (27%), and arthralgia/myalgia (27%) were the commonest adverse events in the A/G arm.

CONCLUSIONS

This phase II study, although prematurely closed, did not show a signal that adding G to A improves PFS at 1 year and its use is not supported. Gastrointestinal and skin toxicities were more pronounced with G resulting in premature therapy interruption in almost 1 in 3 patients (ClinicalTrials.gov number, NCT00066378).

Biological effects of fulvestrant on estrogen receptor positive human breast cancer: short, medium and long-term effects based on sequential biopsies

We report the first study of the biological effect of fulvestrant on ER positive clinical breast cancer using sequential biopsies through to progression. Thirty-two locally/systemically advanced breast cancers treated with first-line fulvestrant (250 mg/month) were biopsied at therapy initiation, 6 weeks, 6 months and progression and immunohistochemically-analyzed for Ki67, ER, EGFR and HER2 expression/signaling activity. This series showed good fulvestrant responses (duration of response [DoR] = 25.8 months; clinical benefit = 81%). Ki67 fell (p < 0.001) in 79% of tumours by 6 months and lower Ki67 at all preprogression time-points predicted for longer DoR. ER and PR significantly decreased in all tumours by 6 months (p < 0.001), with some declines in ER (serine 118) phosphorylation and Bcl-2 (p = 0.007). There were modest HER2 increases (p = 0.034, 29% tumours) and loss of any detectable EGFR phosphorylation (p = 0.024, 50% tumours) and MAP kinase (ERK1/2) phosphorylation (p = 0.019, 65% tumours) by 6 months. While ER remained low, there was some recovery of Ki67, Bcl-2 and (weakly) EGFR/MAPK activity in 45-67% patients at progression. Fulvestrant's anti-proliferative impact is related to DoR, but while commonly downregulating ER and indicators of its signaling and depleting EGFR/MAPK signaling in some patients, additional elements must determine response duration. Residual ER at fulvestrant relapse explains reported sensitivity to further endocrine therapies. Occasional modest treatment-induced HER2 and weakly detectable EGFR/HER2/MAPK signaling at relapse suggests targeting of such activity might have value alongside fulvestrant in some patients. However, unknown pathways must drive relapse in most. Ki67 has biomarker potential to predict fulvestrant outcome and as a quantitative measure of response.

Treatment patterns and duration in post-menopausal women with HR+/HER2- metastatic breast cancer in the US: a retrospective chart review in community oncology practices (2004-2010)

BACKGROUND

Clinical guidelines prefer endocrine therapy (ET) as initial treatment for post-menopausal women with hormone receptor positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer (mBC). Chemotherapy (CT) should be reserved for patients who develop symptomatic visceral disease or have no clinical benefit after three sequential ET regimens. It is unclear if real-world clinical practice reflects these guidelines.

OBJECTIVE

To describe treatment patterns and treatment durations by lines of therapy for ET and CT among post-menopausal HR+/HER2- mBC patients.

METHODS

Charts were reviewed from a network of community-based oncology practices of eligible patients who had progressed after initiating adjuvant or first-line treatment for mBC between 1 January 2004 and 30 September 2010. Extracted chart data included demographics, treatment histories, and outcomes. Treatment duration was estimated using Kaplan-Meier estimators.

RESULTS

A total of 144 patients were studied. Patients received a median of two lines of ET, and <10% had three or more lines of ET before receiving CT. From first line to second line, the median treatment duration was 11.6 to 4.9 months for ET overall; 13.8 to 10.5 months for anastrozole; 18.6 to 7.0 months for letrozole; and 5.1 to 2.9 months for fulvestrant. For CT, the median duration was 5.1 months in the first line and 3.7 months and below in subsequent lines.

CONCLUSION

During the study period (1 January 2004 - 30 September 2012), most patients received <3 lines of ET before receiving CT. The drop in median duration of ET from first to second line suggests that single agent ETs might not be as effective beyond the first line. A key limitation of this study was the small sample size. In addition, more research is needed to further investigate the short treatment duration of fulvestrant across early lines of therapy (which could indicate lack of efficacy).

Receptor tyrosine kinases: Characterisation, mechanism of action and therapeutic interests for bone cancers

Bone cancers are characterised by the development of tumour cells in bone sites, associated with a dysregulation of their environment. In the last two decades, numerous therapeutic strategies have been developed to target the cancer cells or tumour niche. As the crosstalk between these two entities is tightly controlled by the release of polypeptide mediators activating signalling pathways through several receptor tyrosine kinases (RTKs), RTK inhibitors have been designed. These inhibitors have shown exciting clinical impacts, such as imatinib mesylate, which has become a reference treatment for chronic myeloid leukaemia and gastrointestinal tumours. The present review gives an overview of the main molecular and functional characteristics of RTKs, and focuses on the clinical applications that are envisaged and already assessed for the treatment of bone sarcomas and bone metastases.

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.

Current status of hormone therapy in patients with hormone receptor positive (HR+) advanced breast cancer

The natural history of HR+ breast cancer tends to be different from hormone receptor-negative disease in terms of time to recurrence, site of recurrence and overall aggressiveness of the disease. The developmental strategies of hormone therapy for the treatment of breast cancer have led to the classes of selective estrogen receptor modulators, selective estrogen receptor downregulators, and aromatase inhibitors. These therapeutic options have improved breast cancer outcomes in the metastatic setting, thereby delaying the need for chemotherapy. However, a subset of hormone receptor-positive breast cancers do not benefit from endocrine therapy (intrinsic resistance), and all HR+ metastatic breast cancers ultimately develop resistance to hormonal therapies (acquired resistance). Considering the multiple pathways involved in the HR network, targeting other components of pathologically activated intracellular signaling in breast cancer may prove to be a new direction in clinical research. This review focuses on current and emerging treatments for HR+ metastatic breast cancer.

Evolution of breast cancer therapeutics: Breast tumour kinase’s role in breast cancer and hope for breast tumour kinase targeted therapy

There have been significant improvements in the detection and treatment of breast cancer in recent decades. However, there is still a need to develop more effective therapeutic techniques that are patient specific with reduced toxicity leading to further increases in patients’ overall survival; the ongoing progress in understanding recurrence, resistant and spread also needs to be maintained. Better understanding of breast cancer pathology, molecular biology and progression as well as identification of some of the underlying factors involved in breast cancer tumourgenesis and metastasis has led to the identification of novel therapeutic targets. Over a number of years interest has risen in breast tumour kinase (Brk) also known as protein tyrosine kinase 6; the research field has grown and Brk has been described as a desirable therapeutic target in relation to tyrosine kinase inhibition as well as disruption of its kinase independent activity. This review will outline the current “state of play” with respect to targeted therapy for breast cancer, as well as discussing Brk’s role in the processes underlying tumour development and metastasis and its potential as a therapeutic target in breast cancer.

Emerging EGFR antagonists for breast cancer

INTRODUCTION

The EGFR has been associated with the pathogenesis and progression of breast cancer. Treatment based on an EGFR target is emerging as a promising option, especially in combination with conventional therapies. Unfortunately, there are no validated predictor biomarkers, and combinatorial treatments are meeting new resistance.

AREAS COVERED

The purpose of this review is to summarize the existing treatments and the current research based on targeting the EGFR pathway.

EXPERT OPINION

The existing EGFR treatments in breast cancer have shown limited benefit. The combination of the monoclonal antibody cetuximab and platinum salts achieves a 15 - 20% response rate. The effectiveness of tyrosine kinase inhibitors is not completely clear, showing modest or no benefits. Gefitinib treatment has offered some promising results in estrogen receptor + breast cancer. However, it has not been identified as a predictive factor for the appropriate selection of patients. Radioimmunotherapy with anti-EGFR radiolabeled antibodies is a promising strategy in BRCA-mutated breast cancer, but it still requires clinical confirmation. Nevertheless, the crosstalk between pathways frequently leads to treatment resistance. Current research is focused on increasing knowledge about the mechanisms of response and the discovery of predictive markers. Targeting several pathways simultaneously and a correct selection of patients seem essential.

Fulvestrant treatment alters MDM2 protein turnover and sensitivity of human breast carcinoma cells to chemotherapeutic drugs

The human homologue of mouse double minute 2 (MDM2) is overexpressed in tumors and contributes to tumorigenesis through inhibition of p53 activity. We investigated the effect of the anti-estrogen fulvestrant on MDM2 expression and sensitivity of estrogen receptor positive human breast cancer cell lines to chemotherapeutics. Fulvestrant down-regulated MDM2 through increased protein turnover. Fulvestrant blocked estrogen-dependent up-regulation of MDM2 and decreased basal expression of MDM2 in the absence of estradiol. As combinations of fulvestrant with doxorubicin, etoposide or paclitaxel were synergistic, altering cell cycle distribution and increasing cell death, this provides rationale for testing combinatorial chemotherapy with fulvestrant as a novel therapeutic strategy for patients with advanced breast cancer.

Targeting multiple pathways in breast cancer

SUMMARY Breast cancer (BC) is a highly prevalent disease. Worldwide, it is the most common cancer diagnosed and the leading cause of cancer death in women, making this disease a very important focus of interest and research. There is great heterogeneity in clinical outcomes among women diagnosed with BC, possibly indicating that biological heterogeneity is a major factor interfering with tumor development and progression. Presently, it is known that specific genetic expression patterns divide BC into distinct molecular subtypes. In fact, a better understanding of molecular profiles in BC and more advances in biological technology has divided each BC subtype further into additional subcategories. This means that more pathways are being recognized as important drivers or contributors to BC development and progression. The implication in BC treatment and management can be enormous. A more complete knowledge of the biology of the tumor has many implications. Development of therapies that specifically target the activated pathways can allow the delivery of more effective treatments and spare patients from treatments that would only cause side effects. This article will focus on exploring and reviewing the different molecular pathways involved in each clinically relevant BC subtype, namely hormone receptor-positive, HER2-positive and triple-negative BC. For each BC subtype, novel targeted therapies that are already incorporated in clinical practice, as well as drugs in clinical development, will be described, including the safety profiles of each one. We will highlight the major molecular pathways involved in each BC subtype, providing a rationale for the development of specific targeted therapies. Mechanisms of resistance to conventional therapies by pathway activation will be discussed. Strategies to overcome resistance are also a major focus of this review.

Fulvestrant increases gefitinib sensitivity in non-small cell lung cancer cells by upregulating let-7c expression

Patients with non-small cell lung cancer (NSCLC) who have activating epidermal growth factor receptor (EGFR) mutations benefit from treatment with EGFR-tyrosine kinase inhibitors (EGFR-TKIs), namely, gefitinib and erlotinib. However, these patients eventually develop resistance to EGFR-TKIs. About 50% of this acquired resistance may be the result of a secondary mutation in the EGFR gene, such as the one corresponding to T790M. In our previous study, we found that combined treatment with fulvestrant and gefitinib decreases the proliferation of H1975 NSCLC cells, compared to treatment with either fulvestrant or gefitinib alone; however, the molecular mechanism for the improved effects of the combination treatment are still unknown. In this study, we confirmed that fulvestrant increases the gefitinib sensitivity of H1975 cells and found that let-7c was most upregulated in the fulvestrant-treated cells. Our data revealed that let-7c increases gefitinib sensitivity by repressing RAS and inactivating the phosphoinositide 3-kinase (PI3K)/AKT and mitogen-activated extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathways. Taken together, our findings suggest that let-7c plays an important role in fulvestrant-induced upregulation of gefitinib sensitivity in H1975 cells.

Critical research gaps and translational priorities for the successful prevention and treatment of breast cancer

INTRODUCTION

Breast cancer remains a significant scientific, clinical and societal challenge. This gap analysis has reviewed and critically assessed enduring issues and new challenges emerging from recent research, and proposes strategies for translating solutions into practice.

METHODS

More than 100 internationally recognised specialist breast cancer scientists, clinicians and healthcare professionals collaborated to address nine thematic areas: genetics, epigenetics and epidemiology; molecular pathology and cell biology; hormonal influences and endocrine therapy; imaging, detection and screening; current/novel therapies and biomarkers; drug resistance; metastasis, angiogenesis, circulating tumour cells, cancer 'stem' cells; risk and prevention; living with and managing breast cancer and its treatment. The groups developed summary papers through an iterative process which, following further appraisal from experts and patients, were melded into this summary account.

RESULTS

The 10 major gaps identified were: (1) understanding the functions and contextual interactions of genetic and epigenetic changes in normal breast development and during malignant transformation; (2) how to implement sustainable lifestyle changes (diet, exercise and weight) and chemopreventive strategies; (3) the need for tailored screening approaches including clinically actionable tests; (4) enhancing knowledge of molecular drivers behind breast cancer subtypes, progression and metastasis; (5) understanding the molecular mechanisms of tumour heterogeneity, dormancy, de novo or acquired resistance and how to target key nodes in these dynamic processes; (6) developing validated markers for chemosensitivity and radiosensitivity; (7) understanding the optimal duration, sequencing and rational combinations of treatment for improved personalised therapy; (8) validating multimodality imaging biomarkers for minimally invasive diagnosis and monitoring of responses in primary and metastatic disease; (9) developing interventions and support to improve the survivorship experience; (10) a continuing need for clinical material for translational research derived from normal breast, blood, primary, relapsed, metastatic and drug-resistant cancers with expert bioinformatics support to maximise its utility. The proposed infrastructural enablers include enhanced resources to support clinically relevant in vitro and in vivo tumour models; improved access to appropriate, fully annotated clinical samples; extended biomarker discovery, validation and standardisation; and facilitated cross-discipline working.

CONCLUSIONS

With resources to conduct further high-quality targeted research focusing on the gaps identified, increased knowledge translating into improved clinical care should be achievable within five years.

Fulvestrant regulates epidermal growth factor (EGF) family ligands to activate EGF receptor (EGFR) signaling in breast cancer cells

Estrogen receptor-α (ER) targeted therapies are routinely used to treat breast cancer. However, patient responses are limited by resistance to endocrine therapy. Breast cancer cells resistant to the pure steroidal ER antagonist fulvestrant (fulv) demonstrate increased activation of epidermal growth factor receptor (EGFR) family members and downstream ERK signaling. In this study, we investigated the effects of fulv on EGFR signaling and ligand regulation in several breast cancer cell lines. EGFR/HER2/HER3 phosphorylation and ERK1,2 activation were seen after 24-48 h after fulvestrant treatment in ER-positive breast cancer cell lines. 4-Hydroxy-tamoxifen and estradiol did not cause EGFR activation. Fulvestrant did not affect EGFR expression. Cycloheximide abolished the ability of fulv to activate EGFR suggesting the autocrine production of EGFR ligands might be responsible for fulvestrant induced EGFR signaling. qRT-PCR results showed fulv differentially regulated EGFR ligands; HB-EGF mRNA was increased, while amphiregulin and epiregulin mRNAs were decreased. Fulvestrant induced EGFR activation and upregulation of EGFR ligands were ER dependent since fulv treatment in C4-12, an ER-negative cell line derivative of MCF-7 cells, did not result in EGFR activation or change in ligand mRNA levels. ER downregulation by siRNA induced similar EGFR activation and regulation of EGFR ligands as fulvestrant. Neutralizing HB-EGF antibody blocked fulv-induced EGFR activation. Combination of fulv and EGFR family tyrosine kinase inhibitors (erlotinib and lapatinib) significantly decreased EGFR signaling and cell survival. In conclusion, fulvestrant-activated EGFR family members accompanied by ER dependent upregulation of HB-EGF within 48 h. EGF receptor or ligand inhibition might enhance or prolong the therapeutic effects of targeting ER by fulvestrant in breast cancer.

Endocrine resistance in advanced breast cancer: current evidence and future directions

SUMMARY Hormone receptor-positive breast cancer constitutes a heterogeneous group representing the majority (60–75%) of patients with the disease. Hormonal approaches interfering with receptor signaling represents an established treatment strategy with demonstrated efficacy and favorable toxicity profile. However, due to either primary or acquired resistance, metastatic hormone receptor-positive breast cancer remains incurable. Mechanisms of resistance are complex and still poorly understood. Estrogen receptor signaling interactions with critical growth factor pathways and various downstream kinases have been implicated. Available evidence recommends a sequential single-agent approach to advanced hormone receptor-positive disease as a preferred therapeutic alternative. Recent information suggests that rational mTOR inhibition modulates hormonal resistance. Further advances in this field will require analysis of biopsies from metastatic sites at the time of progression.