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

Ongoing unmet needs in treating estrogen receptor-positive/HER2-negative metastatic breast cancer

Estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2 negative (HER2-) advanced or metastatic breast cancer (MBC) is the most common MBC subtype and currently remains incurable, with a median overall survival of 24.8 months (95% confidence interval, 21.3-30.3). Common sites of metastases are bone, viscera, and brain, causing significant symptoms that negatively affect patient functioning, quality of life (QoL), and work productivity. Guidelines state that endocrine therapy (ET) is preferable to chemotherapy as first-line treatment for patients with ER+ MBC, regardless of limited visceral metastases, unless rapid tumor response is required or ET resistance is suspected. Although response rates up to 40% have been reported for first-line MBC treatment, the majority of initial responders eventually develop ET resistance. Notwithstanding the steep decline in efficacy between first and later lines of ET, some patients may receive chemotherapy earlier than necessary. Although new treatments have been approved for patients with ER+/HER2- advanced or MBC in the past decade, neither survival nor QoL appear to have improved significantly. Thus, there remain significant unmet needs for this patient population, including improved survival, maintaining or improving patient QoL, and emphasizing the importance of treatment selection to assist healthcare practitioners managing patient care. In this review, we identify current challenges and unmet needs in this patient population, review cutting-edge treatments, and provide clinically relevant suggestions for treatment selection that can optimize outcomes and patients' health-related QoL.

First-line treatment disruption among post-menopausal women with HR+/HER2- metastatic breast cancer: a retrospective US claims study

OBJECTIVE

This study assessed disruption of first-line treatments initiated after the approval of the first CDK 4/6 inhibitor, palbociclib, among post-menopausal women with HR+/HER2- metastatic breast cancer (mBC) in the US.

METHODS

Post-menopausal women with HR+/HER2- mBC who initiated first-line endocrine therapy or chemotherapy (index therapy) between February 3, 2015 (palbociclib approval date) and February 29, 2016 (end of data) were identified from the Symphony Source Lx database. Patients were required to have continuous quarterly activity (defined as ≥1 pharmacy or medical claim) for 12 months prior to and 1 month after the initiation of the index therapy (index date). Treatment disruption was defined as a treatment gap of ≥60 days or adding an agent after the original therapy. Kaplan-Meier analyses were conducted to estimate treatment disruption rates during the 6 months following the index date. Patients without treatment disruption were censored at the end of continuous quarterly activity or end of data.

RESULTS

A total of 8,160 and 2,153 eligible patients initiated endocrine therapy or chemotherapy as their first-line mBC treatment, with a median follow-up of 6.7 and 7.6 months, respectively. The three most prevalent metastatic sites were bone (28.1-42.2%), liver (8.8-17.3%), and lung (8.6-9.5%). Overall, 37.7% (n = 3,074) of patients receiving endocrine therapy and 86.1% (n = 1,852) of patients receiving chemotherapy encountered treatment disruption at 6 months (log-rank test p < .05).

CONCLUSIONS

Treatment disruption rates of first-line therapies were sub-optimal among post-menopausal women with HR+/HER2- mBC, primarily driven by chemotherapy users. New therapies or interventions are needed to reduce treatment disruption in this patient population.

Trends in progression-free survival (PFS) and time to progression (TTP) over time within first-line aromatase inhibitors trials in hormone receptor-positive advanced breast cancer

BACKGROUND

Over the last 20 years, aromatase inhibitors (AI) have been tested in clinical trials as first-line therapy for hormone receptor-positive (HR-positive) advanced breast cancer (ABC), firstly as experimental arms, when they proved to be effective, and recently as control arms. This analysis aims to evaluate trends in progression-free survival (PFS) and time to progression (TTP) over time.

PATIENTS AND METHODS

A literature review was conducted using the MEDLINE database to identify randomized controlled phase II or III trials which reported PFS or TTP of at least one arm using first-line AI HR-positive ABC patients. A linear correlation was used to access the association between the year of the first patient enrolled and the observed PFS/TTP.

RESULTS

The search retrieved 19 trials, accounting for 4552 postmenopausal patients divided into 21 separate AI treatment arms. The PFS/TTP increased from 6 to 9 months in the earlier trials to 13-16 months in the current era, representing an absolute gain of approximately 7 months, without the addition of any other drug. Our analysis showed a positive correlation between the year of the first patient enrolled in these trials and median PFS/TTP reported (R ² = 0.34; p < 0.01). No correlation was found between the year of the first patient included in these trials and other potential prognostic factors such as visceral metastasis at baseline (R ² = 0.26; p = 0.20) or exposure to adjuvant therapy (R ² = 0.05; p = 0.18).

CONCLUSION

Patients treated with first-line AIs in the more recently conducted trials have longer PFS/TTP when compared to their counterparts treated with the same drugs in older studies. These findings have important implications for the estimation of sample size and follow-up periods for the planning of future trials as well as in the translation of the results into clinical practice decisions.

Translational opportunities for broad-spectrum natural phytochemicals and targeted agent combinations in breast cancer

Breast cancer (BC) prevention and therapy in the context of life-style risk factors and biological drivers is a major focus of developmental therapeutics in oncology. Obesity, alcohol, chronic estrogen signaling and smoking have distinct BC precipitating and facilitating effects that may act alone or in combination. A spectrum of signaling events including enhanced oxidative stress and changes in estrogen-receptor (ER)-dependent and -independent signaling drive the progression of BC. Breast tumors modulate ERα/ERβ ratio, upregulate proliferative pathways driven by ERα and HER2 with a parallel loss and/or downregulation of tumor suppressors such as TP53 and PTEN which together impact the efficacy of therapeutic strategies and frequently lead to emergence of drug resistance. Natural phytochemicals modulate oxidative stress, leptin, integrin, HER2, MAPK, ERK, Wnt/β-catenin and NFκB signaling along with regulating ERα and ERβ, thereby presenting unique opportunities for both primary and combinatorial interventions in BC. In this regard, this article focuses on critical analyses of the evidence from multiple studies on the efficacy of natural phytochemicals in BC. In addition, areas in which the combinations of such effective natural phytochemicals with approved and/or developing anticancer agents can be translationally beneficial are discussed to derive evidence-based inference for addressing challenges in BC control and therapy.

Ribociclib plus letrozole versus letrozole alone in patients with de novo HR+, HER2- advanced breast cancer in the randomized MONALEESA-2 trial

PURPOSE

Determine the efficacy and safety of first-line ribociclib plus letrozole in patients with de novo advanced breast cancer.

METHODS

Postmenopausal women with HR+ , HER2- advanced breast cancer and no prior systemic therapy for advanced disease were enrolled in the Phase III MONALEESA-2 trial (NCT01958021). Patients were randomized to ribociclib (600 mg/day; 3 weeks-on/1 week-off) plus letrozole (2.5 mg/day; continuous) or placebo plus letrozole until disease progression, unacceptable toxicity, death, or treatment discontinuation. The primary endpoint was investigator-assessed progression-free survival; predefined subgroup analysis evaluated progression-free survival in patients with de novo advanced breast cancer. Secondary endpoints included safety and overall response rate.

RESULTS

Six hundred and sixty-eight patients were enrolled, of whom 227 patients (34%; ribociclib plus letrozole vs placebo plus letrozole arm: n = 114 vs. n = 113) presented with de novo advanced breast cancer. Median progression-free survival was not reached in the ribociclib plus letrozole arm versus 16.4 months in the placebo plus letrozole arm in patients with de novo advanced breast cancer (hazard ratio 0.45, 95% confidence interval 0.27-0.75). The most common Grade 3/4 adverse events were neutropenia and leukopenia; incidence rates were similar to those observed in the full MONALEESA-2 population. Ribociclib dose interruptions and reductions in patients with de novo disease occurred at similar frequencies to the overall study population.

CONCLUSIONS

Ribociclib plus letrozole improved progression-free survival vs placebo plus letrozole and was well tolerated in postmenopausal women with HR+, HER2- de novo advanced breast cancer.

Recent Advances of Cell-Cycle Inhibitor Therapies for Pediatric Cancer

This review describes the pivotal roles of cell-cycle and checkpoint regulators and discusses development of specific cell-cycle inhibitors for therapeutic use for pediatric cancer. The mechanism of action as well as the safety and tolerability of drugs in pediatric patients, including compounds that target CDK4/CDK6 (palbociclib, ribociclib, and abemaciclib), aurora kinases (AT9283 and MLN8237), Wee1 kinase (MK-1775), KSP (ispinesib), and tubulin (taxanes, vinca alkaloids), are presented. The design of mechanism-based combinations that exploit the cross-talk of signals activated by cell-cycle arrest, as well as pediatric-focused drug development, are critical for the advancement of drugs for rare childhood diseases. Cancer Res; 77(23); 6489-98. ©2017 AACR.

Analysis of Adjuvant Endocrine Therapy in Practice From Electronic Health Record Data of Patients With Breast Cancer

PURPOSE

Adjuvant endocrine therapy is a long-term drug therapy prescribed to prevent recurrence of hormone receptor-positive breast cancer. Data on adjuvant endocrine therapy are reported though clinical trials, which may differ from treatment practice and outcomes in the general population of patients with breast cancer. With secondary use of electronic health record (EHR) data, we summarize adjuvant endocrine treatment practice and outcomes in real-world settings.

METHODS

We analyzed treatment data derived from EHR data on 1,587 patients with stage I to III breast cancer at a National Cancer Institute-designated comprehensive cancer center to learn the frequencies of real-world adjuvant endocrine drug switches and discontinuation and to explore the potential cause for drug switches and discontinuation from medical records. We measured rates of drug use, drug switches, early drug discontinuation, adverse events, recurrence, and death. We also measured adverse events and change in menopause status as potential causes for drug switch and discontinuation.

RESULTS

Within the study population, approximately 49% of patients were lost to follow-up or did not complete adjuvant treatment through 5 years. Fifty-two percent of patients switched to a different endocrine therapy drug during their treatment. We found that age is correlated with drug switches and that adverse events are correlated with drug switches and discontinuation. We also found that patients who switched to an alternative endocrine therapy during treatment were more likely to complete 5 years of treatment.

CONCLUSION

This study describes long-term adjuvant endocrine treatment in real-world settings and demonstrates the ability to leverage longitudinal EHR data to characterize oral medication treatment patterns in patients with cancer.

Hormonal Changes and Sexual Dysfunction

Sexual dysfunction is a common concern for many patients with cancer after treatment. Hormonal changes as a result of cancer-directed therapy can affect both male and female sexual health. This has the potential to significantly impact patients' quality of life, but is underreported and undertreated in the oncology setting. This review discusses commonly reported sexual issues and the role that hormonal changes play in this dysfunction. Although medical and psychosocial intervention strategies exist, there is a clear need for further research to formally develop programming that can assist people whose sexual health has been impacted by cancer treatment.

Ribociclib with letrozole vs letrozole alone in elderly patients with hormone receptor-positive, HER2-negative breast cancer in the randomized MONALEESA-2 trial

Purpose

Determine the efficacy and safety of first-line ribociclib plus letrozole in elderly patients with HR+, HER2− advanced breast cancer.

Methods

668 postmenopausal women with HR+, HER2− advanced breast cancer and no prior systemic therapy for advanced disease were enrolled in the Phase III MONALEESA-2 trial (NCT01958021); 295 patients were aged ≥ 65 years. Patients were randomized to ribociclib (600 mg/day; 3-weeks-on/1-week-off) plus letrozole (2.5 mg/day) or placebo plus letrozole until disease progression, unacceptable toxicity, death, or treatment discontinuation. The primary endpoint was PFS, which was evaluated in elderly (≥ 65 years) and younger (< 65 years) patients. Secondary endpoints included response rates and safety.

Results

Ribociclib plus letrozole significantly improved PFS vs placebo plus letrozole in elderly (hazard ratio: 0.608; 95% CI 0.394–0.937) and younger patients (hazard ratio: 0.523; 95% CI 0.378–0.723). Overall response rates were numerically higher in the ribociclib vs placebo arm, regardless of age. Ribociclib plus letrozole was well tolerated in elderly patients, with the safety profile similar to the overall study population. Nausea, vomiting, alopecia, and diarrhea were > 10% more frequent in the ribociclib plus letrozole vs placebo plus letrozole arm in both subgroups; most events were grade 1/2. In elderly patients, grade 1/2 anemia and fatigue were > 10% more frequent in the ribociclib plus letrozole vs placebo plus letrozole arm and discontinuation rates were similar in both arms.

Conclusions

Addition of ribociclib to letrozole is a valid therapeutic option for elderly patients with HR+, HER2− advanced breast cancer in the first-line setting.

CIP2A expression predicts recurrences of tamoxifen-treated breast cancer

CIP2A is emerging as an oncoprotein overexpressed commonly across many tumours and generally correlated with higher tumour grade and therapeutic resistance. CIP2A drives an oncogenic potential through inhibiting protein phosphatase 2A, stabilizing MYC, and promoting epithelial-to-mesenchymal transition, although further biological mechanisms for CIP2A are yet to be defined. CIP2A protein expression was studied by immunohistochemistry in oestrogen receptor-positive primary breast cancers (n = 250) obtained from the Leeds Tissue Bank. In total, 51 cases presented with a relapse or metastasis during adjuvant treatment with tamoxifen and were regarded as tamoxifen resistant. CIP2A expression was scored separately for cytoplasmic, nuclear, or membranous staining, and scores were tested for statistically significant relationships with clinicopathological features. Membranous CIP2A was preferentially expressed in cases who experienced a recurrence during tamoxifen treatment thus predicting a worse overall survival (log rank = 8.357, p = 0.004) and disease-free survival (log rank = 21.766, p < 0.001). Cox multivariate analysis indicates that it is an independent prognostic indicator for overall survival (hazard ratio = 4.310, p = 0.013) and disease-free survival (hazard ratio = 5.449, p = 0.002). In this study, we propose the assessment of membranous CIP2A expression as a potential novel prognostic and predictive indicator for tamoxifen resistance and recurrence within oestrogen receptor-positive breast cancer.

The next era of treatment for hormone receptor-positive, HER2-negative advanced breast cancer: Triplet combination-based endocrine therapies

Until recently, the standard of care for hormone receptor-positive (HR+) breast cancer was single-agent endocrine therapy, which aims to prevent estrogen receptor signaling. This therapeutic strategy has extended survival without the toxicity associated with chemotherapy, but primary endocrine therapy resistance is common, and secondary resistance develops over time. Adjunct downstream inhibition of the cyclin-dependent kinase (CDK)4/6 pathway, intended to delay and prevent endocrine therapy resistance, has further extended progression-free survival in patients receiving endocrine therapy; however, resistance still eventually develops in these patients. Addition of phosphatidylinositol-3 kinase (PI3K) or mammalian target of rapamycin (mTOR) inhibitors to combined CDK4/6 and endocrine inhibitor regimens may help prolong CDK4/6 inhibitor sensitivity. Early trials combining CDK4/6 inhibitors, PI3K or mTOR inhibitors, and endocrine therapy have shown encouraging signs of clinical activity. However, further research is needed to help understand the extent of treatment benefit from triplet therapy and where this strategy will fit in the treatment sequence for patients with HR+ breast cancer.

Predictive Value of Circulating Tumor Cells for Evaluating Short- and Long-Term Efficacy of Chemotherapy for Breast Cancer

BACKGROUND The present study investigated the role of circulating tumor cells (CTCs) counts in predicting the short- and long-term efficacy of chemotherapy for breast cancer (BC). MATERIAL AND METHODS Peripheral venous blood was extracted from 187 BC patients. CTCs were measured by flow cytometry. Spearman's correlation analysis was performed to examine the correlation between the efficacy of chemotherapy and CTC counts. A receiver operating characteristic (ROC) curve was plotted to estimate the predictive value of CTC counts. The Kaplan-Meier method was employed to calculate disease-free survival (DFS) and overall survival (OS). Cox regression analysis was used to determine risk factors for prognosis of BC. RESULTS Complete response (CR) + partial response (PR) was achieved by 65.8% of BC patients. After chemotherapy, CTC counts were decreased in both the CR + PR and SD + PD groups. Spearman's correlation analysis indicated that CTC counts before chemotherapy were positively correlated with clinical response to chemotherapy (r=0.45, P<0.05). For predicting clinical response to chemotherapy, CTC counts yielded an area under the curve (AUC) of 0.958, with sensitivity reaching 96.9% and specificity reaching 85.4%. The Kaplan-Meier method and Cox regression analysis indicated that tumor node metastasis (TNM) staging, lymph node metastasis (LNM), ki-67, endocrine therapy, and CTC counts were risk factors for prognosis of BC. CONCLUSIONS These findings indicate that BC patients with CTCs ³8 exhibited poor response to chemotherapy and poor OS. CTC counts can serve as an indicator in predicting short- and long-term efficacy of chemotherapy for BC.

Incorporating CDK4/6 Inhibitors in the Treatment of Advanced Luminal Breast Cancer

After optimizing endocrine monotherapy modalities in the setting of advanced luminal breast cancer (BC), dual endocrine/targeted therapy combinations have been tested with positive results, and are transforming this BC subtype treatment landscape. Cell cycle deregulation is a hallmark of cancer that has become a key druggable target in hormone receptor (HR)-positive BC due to its role in endocrine resistance mechanisms. Cyclin dependent kinase (CDK)4/6 inhibitors have experienced a fast development in combination with endocrine therapy and have already been commercialized in some countries. In this review, we will summarize the development of these CDK4/6 inhibitors in luminal BC, from the preclinical data to the pivotal phase III trials that led to their approval, focusing on the efficacy and safety data for each of the treatment settings. Moreover, we will consider the challenges CDK4/6 inhibitors face in their positioning in the algorithm of treatment for advanced luminal BC and the considerations physicians should take into account when selecting these therapies for their patients. However, we are still in need of reliable predictive biomarkers in order to identify patients who will derive the greatest benefit from these drug combinations that are not exempt from toxicity.

The Role of Gonadotropin-Releasing-Hormone Analogues in the Treatment of Breast Cancer

The prognosis of premenopausal breast cancer patients with early disease has improved over the past decades, particularly in women expressing hormone receptors in their tumors. Tamoxifen, a selective estrogen receptor modulator, has dramatically changed outcomes in these patients and remains one of the standards of care. Ovarian function suppression by gonadotropin-releasing-hormone analogues (GnRHa) represents an additional treatment option. Long-term data are required before firm conclusions can be drawn, whereas recent clinical trials suggest that the use of GnRHa is effective in both adjuvant and metastatic settings, particularly in younger patients (<35 years old). The decision to select the optimal therapy should be individualized according to the biological characteristics of tumors, estimates of disease response, comorbidities, patient preference, and long-term toxicity.

Palbociclib in hormone receptor positive advanced breast cancer: A cost-utility analysis

INTRODUCTION

The addition of palbociclib to letrozole improves progression-free survival in the first-line treatment of hormone receptor positive advanced breast cancer (ABC). This study assesses the cost-utility of palbociclib from the Canadian healthcare payer perspective.

METHODS

A probabilistic discrete event simulation (DES) model was developed and parameterised with data from the PALOMA 1 and 2 trials and other sources. The incremental cost per quality-adjusted life-month (QALM) gained for palbociclib was calculated. A time horizon of 15 years was used in the base case with costs and effectiveness discounted at 5% annually. Time-to- progression and time-to-death were derived from a Weibull and exponential distribution. Expected costs were based on Ontario fees and other sources. Probabilistic sensitivity analyses were conducted to account for parameter uncertainty.

RESULTS

Compared to letrozole, the addition of palbociclib provided an additional 14.7 QALM at an incremental cost of $161,508. The resulting incremental cost-effectiveness ratio was $10,999/QALM gained. Assuming a willingness-to-pay (WTP) of $4167/QALM, the probability of palbociclib to be cost-effective was 0%. Cost-effectiveness acceptability curves derived from a probabilistic sensitivity analysis showed that at a WTP of $11,000/QALM gained, the probability of palbociclib to be cost-effective was 50%.

CONCLUSION

The addition of palbociclib to letrozole is unlikely to be cost-effective for the treatment of ABC from a Canadian healthcare perspective with its current price. While ABC patients derive a meaningful clinical benefit from palbociclib, considerations should be given to increase the WTP threshold and reduce the drug pricing, to render this strategy more affordable.

Re-inventing drug development: A case study of the I-SPY 2 breast cancer clinical trials program

BACKGROUND

In this case study, we profile the I-SPY 2 TRIAL (Investigation of Serial studies to Predict Your Therapeutic Response with Imaging And molecular anaLysis 2), a unique breast cancer clinical trial led by researchers at 20 leading cancer centers across the US, and examine its potential to serve as a model of drug development for other disease areas. This multicenter collaboration launched in 2010 to reengineer the drug development process to be more efficient and patient-centered.

METHODS

We conduct several interviews with the I-SPY leadership as well as a literature review of relevant publications to assess the I-SPY 2 initiative.

RESULTS

To date, six drugs have graduated from I-SPY 2, identified as excellent candidates for phase 3 trials in their corresponding tumor subtype, and several others have been or are still being evaluated. These trials are also more efficient, typically involving fewer subjects and reaching conclusions more quickly, and candidates have more than twice the predicted likelihood of success in a smaller phase 3 setting compared to traditional trials.

CONCLUSIONS

We observe that I-SPY 2 possesses several novel features that could be used as a template for more efficient and cost effective drug development, namely its adaptive trial design; precompetitive network of stakeholders; and flexible infrastructure to accommodate innovation.

MONARCH 2: Abemaciclib in Combination With Fulvestrant in Women With HR+/HER2− Advanced Breast Cancer Who Had Progressed While Receiving Endocrine Therapy

Purpose

MONARCH 2 ( ClinicalTrials.gov identifier: NCT02107703) compared the efficacy and safety of abemaciclib, a selective cyclin-dependent kinase 4 and 6 inhibitor, plus fulvestrant with fulvestrant alone in patients with advanced breast cancer (ABC).

Patients and Methods

MONARCH 2 was a global, double-blind, phase III study of women with hormone receptor-positive and human epidermal growth factor receptor 2-negative ABC who had progressed while receiving neoadjuvant or adjuvant endocrine therapy (ET), ≤ 12 months from the end of adjuvant ET, or while receiving first-line ET for metastatic disease. Patients were randomly assigned 2:1 to receive abemaciclib or placebo (150 mg twice daily) on a continuous schedule and fulvestrant (500 mg, per label). The primary end point was investigator-assessed progression-free survival (PFS), and key secondary end points included overall survival, objective response rate (ORR), duration of response, clinical benefit rate, quality of life, and safety.

Results

Between August 2014 and December 2015, 669 patients were randomly assigned to receive abemaciclib plus fulvestrant (n = 446) or placebo plus fulvestrant (n = 223). Abemaciclib plus fulvestrant significantly extended PFS versus fulvestrant alone (median, 16.4 v 9.3 months; hazard ratio, 0.553; 95% CI, 0.449 to 0.681; P < .001). In patients with measurable disease, abemaciclib plus fulvestrant achieved an ORR of 48.1% (95% CI, 42.6% to 53.6%) compared with 21.3% (95% CI, 15.1% to 27.6%) in the control arm. The most common adverse events in the abemaciclib versus placebo arms were diarrhea (86.4% v 24.7%), neutropenia (46.0% v 4.0%), nausea (45.1% v 22.9%), and fatigue (39.9% v 26.9%).

Conclusions

Abemaciclib at 150 mg twice daily plus fulvestrant was effective, significantly improving PFS and ORR and demonstrating a tolerable safety profile in women with hormone receptor-positive and human epidermal growth factor receptor 2-negative ABC who progressed while receiving ET.

Patient-reported pain severity, pain interference and health status in HR+/HER2- advanced/metastatic breast cancer

Introduction

Patient-reported pain severity and related impact in advanced/metastatic breast cancer (ABC/MBC) are not well documented. The objective of this study was to assess pain and general health status in hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2−) ABC/MBC.

Methods

Data were collected in the USA and Europe in a real-world, cross-sectional study. Patients were recruited at oncology practices and completed validated questionnaires; pain severity and interference were assessed using the Brief Pain Inventory (BPI) and general health status using the EuroQoL-5D (EQ-5D-3L). Descriptive statistics were generated for the overall cohort, and stratified by type of therapy and sites of metastases. Differences between patient groups were assessed via the Mann-Whitney Wilcoxon test. The relationship between pain scores and general health status was assessed using Kruskal-Wallis tests.

Results

Overall, 173 oncologists and 739 patients participated. The majority of patients rated their worst pain, average pain and pain interference as mild (59%, 77% and 70%, respectively). Most patients (>90%) reported no problems or moderate problems for all items of the EQ-5D-3L. Current treatment had no significant associations with pain severity or interference. Patients on chemotherapy reported significantly higher proportions of moderate/extreme levels of anxiety/depression (66.7%) and significantly lower general health status (60.7) compared with those on endocrine therapy (53.1% and 64.4, respectively). Pain severity and interference, all EQ-5D-3L items except self-care and the EQ-5D-3L health utility index were also significantly associated with sites of metastases, with greater impact in patients with visceral and bone metastases than those with bone only or visceral only metastases. Significant associations were observed between pain and health status, with increased pain severity and pain interference associated with worse health utility and general health status.

Conclusion

There is a clear unmet need for treatments that can reduce pain and preserve health status in patients with HR+/HER2− ABC/MBC.

MicroRNA-mediated drug resistance in ovarian cancer

The development of intrinsic or acquired resistance to chemotherapeutic agents used in the treatment of various human cancers is a major obstacle for the successful abolishment of cancer. The accumulated efforts in the understanding the exact mechanisms of development of multidrug resistance (MDR) have led to the introduction of several unique and common mechanisms. Recent studies demonstrate the regulatory role of small noncoding RNA or miRNA in the several parts of cancer biology. Practically all aspects of cell physiology under normal and disease conditions are reported to be controlled by miRNAs. In this review, we discuss how the miRNA profile is changed upon MDR development and the pivotal regulatory role played by miRNAs in overcoming resistance to chemotherapeutic agents. It is hoped that further studies will support the use of these differentially expressed miRNAs as prognostic and predictive markers, as well as novel therapeutic targets to overcome resistance in ovarian cancer.

Long-term management of patients with hormone receptor-positive metastatic breast cancer: Concepts for sequential and combination endocrine-based therapies

Treatment options for hormone receptor-positive (HR-positive) metastatic breast cancer (MBC) continue to increase in parallel with expanding knowledge about the complex biology of breast cancer subtypes and resistance mechanisms to endocrine therapy. For patients with HR-positive MBC, there are now an unprecedented number of endocrine-based treatment options that can improve long-term outcomes, while preserving or optimizing quality of life, and that can be used before selecting more cytotoxic chemotherapeutic regimens. In addition to antiestrogens, steroidal and nonsteroidal aromatase inhibitors, the selective estrogen-receptor degrader, fulvestrant, and new endocrine-based combinations provide significant and clinically meaningful improvements in outcomes in the first line setting and beyond. Also, new clinical scenarios and indications for monotherapy endocrine and targeted therapies continue to be explored. Patients have several therapeutic options when their disease progresses or becomes resistant, although the optimal sequencing of these therapies remains unclear. Ongoing research in the resistant/refractory setting is anticipated to continue improving the outlook for these patients. This review will discuss current and investigational approaches to sequential single-agent endocrine and endocrine-based combination therapy for the long-term management of patients with HR-positive, human epidermal growth factor receptor 2-negative MBC.

Palbociclib Combined with Fulvestrant in Premenopausal Women with Advanced Breast Cancer and Prior Progression on Endocrine Therapy: PALOMA-3 Results

BACKGROUND

The efficacy and safety of palbociclib, a cyclin-dependent kinase 4/6 inhibitor, combined with fulvestrant and goserelin was assessed in premenopausal women with advanced breast cancer (ABC) who had progressed on prior endocrine therapy (ET).

PATIENTS AND METHODS

One hundred eight premenopausal endocrine-refractory women ≥18 years with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) ABC were among 521 women randomized 2:1 (347:174) to fulvestrant (500 mg) ± goserelin with either palbociclib (125 mg/day orally, 3 weeks on, 1 week off) or placebo. This analysis assessed whether the overall tolerable safety profile and significant progression-free survival (PFS) improvement extended to premenopausal women. Potential drug-drug interactions (DDIs) and ovarian suppression with goserelin were assessed via plasma pharmacokinetics and biochemical analyses, respectively. (ClinicalTrials.gov identifier: NCT01942135) RESULTS: Median PFS for premenopausal women in the palbociclib (n = 72) versus placebo arm (n = 36) was 9.5 versus 5.6 months, respectively (hazard ratio, 0.50, 95% confidence interval: 0.29-0.87), and consistent with the significant PFS improvement in the same arms for postmenopausal women. Any-grade and grade ≤3 neutropenia, leukopenia, and infections were among the most frequent adverse events reported in the palbociclib arm with concurrent goserelin administration. Hormone concentrations were similar between treatment arms and confirmed sustained ovarian suppression. Clinically relevant DDIs were not observed.

CONCLUSION

Palbociclib combined with fulvestrant and goserelin was an effective and well-tolerated treatment for premenopausal women with prior endocrine-resistant HR+/HER2- ABC. Inclusion of both premenopausal and postmenopausal women in pivotal combination ET trials facilitates access to novel drugs for young women and should be considered as a new standard for clinical trial design.

IMPLICATIONS FOR PRACTICE

PALOMA-3, the first registrational study to include premenopausal women in a trial investigating a CDK4/6 inhibitor combined with endocrine therapy, has the largest premenopausal cohort reported in an endocrine-resistant setting. In pretreated premenopausal women with hormone receptor-positive advanced breast cancer, palbociclib plus fulvestrant and goserelin (luteinizing hormone-releasing hormone [LHRH] agonist) treatment almost doubled median progression-free survival (PFS) and significantly increased the objective response rate versus endocrine monotherapy, achieving results comparable to those reported for chemotherapy without apparently interfering with LHRH agonist-induced ovarian suppression. The significant PFS gain and tolerable safety profile strongly support use of this regimen in premenopausal women with endocrine-resistant disease who could possibly delay chemotherapy.

Fulvestrant in advanced breast cancer: evidence to date and place in therapy

Breast cancer is a classical hormone-dependent tumour; therefore, endocrine therapy is the mainstay of treatment for hormone receptor-positive, human epidermal growth factor 2-negative advanced breast cancer. Until recently, classical endocrine agents such as tamoxifen, steroidal and nonsteroidal aromatase inhibitors and fulvestrant have been widely used in postmenopausal patients to treat locally advanced or metastatic disease. However, for patients with this subtype of breast cancer, the landscape of endocrine therapy is rapidly changing. Therapies targeting oestrogen modulation have evolved in recent years following the introduction of targeted agents, mTOR and CDK 4/6 inhibitors that are administered in combination with hormone therapy. As a result, options for endocrine therapy have expanded in recent years, and a variety of single-agent or combinations of targeted drugs and endocrine therapies are accepted. Fulvestrant is a selective oestrogen receptor downregulator (SERD) which was introduced to clinical practice in 2002, initially with the indication to treat postmenopausal women with hormone-receptor-positive advanced breast cancer as second-line therapy postdisease progression after aromatase inhibitors or tamoxifen. Additionally, fulvestrant has also been shown to be active in patients previously untreated with endocrine therapy, either both in the neoadjuvant and the metastatic setting, alone or in combination with other targeted therapies. Currently, the standard dose is 500 mg, which is administered with a loading dose. Fulvestrant received a new FDA indication in December 2016, in combination with palbociclib, both in pre/peri/postmenopausal women with breast cancer progressing after endocrine therapy.

This manuscript aims to give an overview of new efficacy data and the current role of fulvestrant in the systemic therapy of hormone-receptor-positive advanced breast cancer, in the context of other available therapeutic modalities.

MONARCH 1, A Phase II Study of Abemaciclib, a CDK4 and CDK6 Inhibitor, as a Single Agent, in Patients with Refractory HR+/HER2- Metastatic Breast Cancer

Purpose: The phase II MONARCH 1 study was designed to evaluate the single-agent activity and adverse event (AE) profile of abemaciclib, a selective inhibitor of CDK4 and CDK6, in women with refractory hormone receptor-positive (HR⁺), HER2^- metastatic breast cancer (MBC).Experimental Design: MONARCH 1 was a phase II single-arm open-label study. Women with HR⁺/HER2^- MBC who had progressed on or after prior endocrine therapy and had 1 or 2 chemotherapy regimens in the metastatic setting were eligible. Abemaciclib 200 mg was administered orally on a continuous schedule every 12 hours until disease progression or unacceptable toxicity. The primary objective of MONARCH 1 was investigator-assessed objective response rate (ORR). Other endpoints included clinical benefit rate, progression-free survival (PFS), and overall survival (OS).Results: Patients (n = 132) had a median of 3 (range, 1-8) lines of prior systemic therapy in the metastatic setting, 90.2% had visceral disease, and 50.8% had ≥3 metastatic sites. At the 12-month final analysis, the primary objective of confirmed objective response rate was 19.7% (95% CI, 13.3-27.5; 15% not excluded); clinical benefit rate (CR+PR+SD≥6 months) was 42.4%, median progression-free survival was 6.0 months, and median overall survival was 17.7 months. The most common treatment-emergent AEs of any grade were diarrhea, fatigue, and nausea; discontinuations due to AEs were infrequent (7.6%).Conclusions: In this poor-prognosis, heavily pretreated population with refractory HR⁺/HER2^- metastatic breast cancer, continuous dosing of single-agent abemaciciclib was well tolerated and exhibited promising clinical activity. Clin Cancer Res; 23(17); 5218-24. ©2017 AACR.

Racial Differences in Adjuvant Endocrine Therapy Use and Discontinuation in Association with Mortality among Medicare Breast Cancer Patients by Receptor Status

Background: There are racial disparities in breast cancer mortality. Our purpose was to determine whether racial/ethnic differences in use and discontinuation of adjuvant endocrine therapy (AET) differed by hormone receptor status and whether discontinuation was associated with mortality.Methods: We conducted a retrospective cohort study with SEER/Medicare dataset of women age ≥65 years diagnosed with stage I-III breast cancer in Medicare Part-D from 2007 to 2009, stratified by hormone receptor status. We performed multivariable logistic regressions to assess racial differences for the odds of AET initiation and Cox proportional hazards models to determine the risk of discontinuation and mortality.Results: Of 14,902 women, 64.5% initiated AET <12 months of diagnosis. Among those with hormone receptor-positive cancer, 74.8% initiated AET compared with 5.6% of women with negative and 54.0% with unknown-receptor status. Blacks were less likely to initiate [OR, 0.76; 95% confidence interval (CI), 0.66-0.88] compared with whites. However, those with hormone receptor-positive disease were less likely to discontinue (HR, 0.89; 95% CI, 0.80-0.98). Women who initiated with aromatase inhibitors had increased risk of discontinuation compared with women who initiated tamoxifen (HR, 1.12; 95% CI, 1.05-1.20). Discontinuation within 12 months was associated with higher risk of all-cause (HR, 1.75; 95% CI, 1.74-2.00) and cancer-specific mortality (HR, 2.76; 95% CI, 1.74-4.38) after controlling for race/ethnicity.Conclusions: There are racial/ethnic differences in AET use and discontinuation. Discontinuing treatment was associated with higher risk of all-cause and cancer-specific mortality regardless of hormone receptor status.Impact: This study underscores the need to study factors that influence discontinuation and the survival benefits of receiving AET for hormone receptor-negative breast cancer. Cancer Epidemiol Biomarkers Prev; 26(8); 1266-75. ©2017 AACR.

Prospective assessment of patient-reported outcomes and estradiol and drug concentrations in patients experiencing toxicity from adjuvant aromatase inhibitors

PURPOSE

Aromatase inhibitors (AI), which decrease circulating estradiol concentrations in post-menopausal women, are associated with toxicities that limit adherence. Approximately one-third of patients will tolerate a different AI after not tolerating the first. We report the effect of crossover from exemestane to letrozole or vice versa on patient-reported outcomes (PROs) and whether the success of crossover is due to lack of estrogen suppression.

METHODS

Post-menopausal women enrolled on a prospective trial initiating AI therapy for early-stage breast cancer were randomized to exemestane or letrozole. Those that discontinued for intolerance were offered protocol-directed crossover to the other AI after a washout period. Changes in PROs, including pain [Visual Analog Scale (VAS)] and functional status [Health Assessment Questionnaire (HAQ)], were compared after 3 months on the first versus the second AI. Estradiol and drug concentrations were measured.

RESULTS

Eighty-three patients participated in the crossover protocol, of whom 91.3% reported improvement in symptoms prior to starting the second AI. Functional status worsened less after 3 months with the second AI (HAQ mean change AI #1: 0.2 [SD 0.41] vs. AI #2: -0.05 [SD 0.36]; p = 0.001); change in pain scores was similar between the first and second AI (VAS mean change AI #1: 0.8 [SD 2.7] vs. AI #2: -0.2 [SD 2.8]; p = 0.19). No statistical differences in estradiol or drug concentrations were found between those that continued or discontinued AI after crossover.

CONCLUSIONS

Although all AIs act via the same mechanism, a subset of patients intolerant to one AI report improved PROs with a different one. The mechanism of this tolerance remains unknown, but does not appear to be due to non-adherence to, or insufficient estrogen suppression by, the second AI.

Anthropometric, clinical and molecular determinants of treatment outcomes in postmenopausal, hormone receptor positive metastatic breast cancer patients treated with fulvestrant: Results from a real word setting

To characterize determinants of treatment outcome in a real world population of 161 post-menopausal hormone receptor-positive metastatic breast cancer patients treated with fulvestrant. Descriptive statistics for demographics, anthropometrics, clinical and molecular characteristic were compared across subgroups of sensitivity/resistance to prior endocrine therapy and tested in uni/multivariate models. Clinical benefit was more common in sensitive patients with higher estrogen receptor expression and when fulvestrant was given in first line (p=0.02 and 0.046). In resistant patients, PFS was longer with lower BMI (p=0.01). Among endocrine sensitive women, longer PFS was associated with fulvestrant in first-line, single metastasis and no visceral involvement (p=0.01, 0.003 and 0.01). OS was shorter in resistant patients with HER2-positive disease and if fulvestrant was given in second and subsequent line (p=0.03). In sensitive patients, we observed worse OS with multiple metastases (p=0.008). Multivariate analyses confirmed longer PFS in resistant patients with lower BMI and older age (p=0.002 and 0.007). OS in resistant patients was negatively influenced by HER2 positivity and fulvestrant in second and subsequent line (p=0.04). In sensitive women, multiple metastases were associated with poorer survival (p=0.002). This evidence encourages considering patient and disease characteristics in decision making and outcome interpretation for patients candidate to fulvestrant.

Clinical Implications of ESR1 Mutations in Hormone Receptor-Positive Advanced Breast Cancer

Hormone receptor-positive breast cancer is the most frequent breast cancer subtype. Endocrine therapy (ET) targeting the estrogen receptor (ER) pathway represents the main initial therapeutic approach. The major strategies include estrogen deprivation and the use of selective estrogen modulators or degraders, which show efficacy in the management of metastatic and early-stage disease. However, clinical resistance associated with progression of disease remains a significant therapeutic challenge. Mutations of the ESR1 gene, which encodes the ER, have been increasingly recognized as an important mechanism of ET resistance, with a prevalence that ranges from 11 to 39%. The majority of these mutations are located within the ligand-binding domain and result in an estrogen-independent constitutive activation of the ER and, therefore, resistance to estrogen deprivation therapy such as aromatase inhibition. ESR1 mutations, most often detected from liquid biopsies, have been consistently associated with a worse outcome and are being currently evaluated as a potential biomarker to guide therapeutic decisions. At the same time, targeted therapy directed to ESR1-mutated clones is an appealing concept with preclinical and clinical work in progress.

New Strategies in Metastatic Hormone Receptor-Positive Breast Cancer: Searching for Biomarkers to Tailor Endocrine and Other Targeted Therapies

Although major advances in our understanding of the molecular underpinnings of hormone receptor-positive (HR+) breast cancer have led to new therapies that have substantially improved patient outcomes, endocrine-resistant disease still remains a leading cause of breast cancer mortality. Comprehensive molecular profiling of breast cancers has highlighted tremendous tumor heterogeneity, and analysis of paired primary and metastatic tumors has shown the evolution that can occur during acquired resistance to systemic therapies. Novel techniques for monitoring tumor load under treatment pressure, including "liquid biopsy" techniques, such as circulating free tumor DNA (cfDNA) and circulating tumor cells, have shown promise as biomarkers to direct treatment without invasive tumor biopsies. However, more research is needed to deepen our understanding of breast cancer alterations under treatment pressure to reveal mechanisms of drug resistance and apply precision medicine in biomarker-driven clinical trials. Clin Cancer Res; 23(5); 1126-31. ©2016 AACR.

Bilateral Salpingo-oophorectomy Compared to Gonadotropin-Releasing Hormone Agonists in Premenopausal Hormone Receptor-Positive Metastatic Breast Cancer Patients Treated with Aromatase Inhibitors

Purpose

Although combining aromatase inhibitors (AI) with gonadotropin-releasing hormone agonists (GnRHa) is becoming more common, it is still not clear if GnRHa is as effective as bilateral salpingo-oophorectomy (BSO).

Materials and Methods

We retrospectively analyzed data of 66 premenopausal patients with hormone receptor– positive, human epidermal growth factor receptor 2–negative recurrent and metastatic breast cancer who had been treated with AIs in combination with GnRHa or BSO between 2002 and 2015.

Results

The median patient age was 44 years. Overall, 24 (36%) received BSO and 42 (64%) received GnRHa. The clinical benefit rate was higher in the BSO group than in the GnRHa group (88% vs. 69%, p=0.092). Median progression-free survival (PFS) was longer in the BSO group, although statistical significance was not reached (17.2 months vs. 13.3 months, p=0.245). When propensity score matching was performed, the median PFS was 17.2 months for the BSO group and 8.2 months for the GnRHa group (p=0.137). Multivariate analyses revealed that the luminal B subtype (hazard ratio, 1.67; 95% confidence interval [CI], 1.08 to 2.60; p=0.022) and later-line treatment (≥ third line vs. first line; hazard ratio, 3.24; 95% CI, 1.59 to 6.59; p=0.001) were independent predictive factors for a shorter PFS. Incomplete ovarian suppression was observed in a subset of GnRHa-treated patients whose disease showed progression, with E2 levels higher than 21 pg/mL.

Conclusion

Both BSO and GnRHa were found to be effective in our AI-treated premenopausal metastatic breast cancer patient cohort. However, further studies in larger populations are needed to determine if BSO is superior to GnRHa.

Specific CDK4/6 inhibition in breast cancer: a systematic review of current clinical evidence

BACKGROUND

Loss of cell cycle control is a hallmark of cancer, and aberrations in the cyclin-dependent kinase-retinoblastoma (CDK-Rb) pathway are common in breast cancer (BC). Consequently, inhibition of this pathway is an attractive therapeutic strategy. The present review addresses efficacy and toxicity of CDK4/6 inhibition in BC.

METHODS

A literature search was carried out using PubMed and EMBASE; data reported at international meetings and clinicaltrials.gov were included.

RESULTS

Three specific CDK4/6 inhibitors palbociclib, abemaciclib and ribociclib are tested in clinical trials. A randomised phase II trial of palbociclib plus letrozole versus letrozole and a phase III of palbociclib plus fulvestrant versus fulvestrant showed significantly increased progression-free survival when compared with endocrine therapy alone in first-line and second-line treatment for advanced hormone receptor-positive HER2-negative BC. At the moment several phase III studies are ongoing with all three CDK4/6 inhibitors in hormone receptor-positive HER2-negative BC as well as other subtypes of BC. The predominant toxicity of agents was limited neutropenia. Other common adverse events were infections, fatigue and gastrointestinal toxicity. The toxicities seemed manageable. Yet data are too limited to differentiate between the compounds. Retinoblastoma protein (Rb) is considered a promising biomarker.

CONCLUSION

CDK4/6 inhibition might represent a substantial advance for patients with hormone receptor-positive HER2-negative BC. Results must be confirmed in phase III trials before any firm conclusions can be made regarding the future influence of CDK4/6 inhibition. There is an urgent need for prospective biomarker-driven trials to identify patients for whom CDK4/6 inhibition is cost-effective.

HR+, HER2- Advanced Breast Cancer and CDK4/6 Inhibitors: Mode of Action, Clinical Activity, and Safety Profiles

BACKGROUND

Cyclin-dependent kinase (CDK) 4/6 inhibitor-based therapies have shown great promise in improving clinical outcomes for patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer.

OBJECTIVES

1. Discuss the mode of action of the three CDK4/6 inhibitors in late clinical development: palbociclib (PD-0332991; Pfizer), ribociclib (LEE011; Novartis), and abemaciclib (LY2835219; Lilly). 2. Describe the efficacy and safety data relating to their use in HR+, HER2- advanced breast cancer. 3. Discuss the key side effects associated with CDK4/6 inhibitors along with considerations for adverse event management and patient monitoring.

METHOD

Relevant information and data were assimilated from manuscripts, congress publications, and online sources.

RESULTS

CDK4/6 inhibitors have demonstrated improved progression-free survival in combination with endocrine therapy compared with endocrine therapy alone. The side-effect profile of each agent is described, along with implications for patient monitoring, and considerations for patient care providers and pharmacists.

CONCLUSION

Addition of a CDK4/6 inhibitor to endocrine therapy increases efficacy and delays disease progression. Insight into the unique side-effect profiles of this class of agents and effective patient monitoring will facilitate the successful use of CDK4/6 inhibitor-based therapies in the clinic.

Strategies and Progress of Endocrine Therapy for Patients with Metastatic Breast Cancer

Breast cancer is one of the most prevalent cancers and the leading causes of cancer mortality in women worldwide and in China. For hormone receptor-positive (HR+) breast cancer, accounting for approximately 60-80% of breast cancer, endocrine therapy (ET) is the primary treatment strategy. For patients with HR+ metastatic breast cancer (MBC), there are many endocrine-based treatment options that can improve long-term outcomes and optimize quality of life. With the emergence and availability of new and effective agents, the options for ET have expanded in the last two decades. Although hormone therapy has been a standard of care for many decades, treatment must be individualized based on tumor biology and extent of disease. For example, the patients with impending organ failure may be treated with induction chemotherapy to improve organ function, followed by ET. For the patients who develop metastatic disease while on adjuvant ET, particularly when associated with organ failure, or for those with low expression of hormone receptors or expression of HER2, chemotherapy again may be a preferred initial treatment. ET blocks estrogen-driven tumor growth through different mechanisms; however, HR+ MBC can be intrinsically resistant or may acquire resistance to the treatment. Several targeted agents have been approved to use in combination with ET to improve response and delay development of resistance.

Fulvestrant 500 mg versus anastrozole 1 mg for hormone receptor-positive advanced breast cancer (FALCON): an international, randomised, double-blind, phase 3 trial

BACKGROUND

Aromatase inhibitors are a standard of care for hormone receptor-positive locally advanced or metastatic breast cancer. We investigated whether the selective oestrogen receptor degrader fulvestrant could improve progression-free survival compared with anastrozole in postmenopausal patients who had not received previous endocrine therapy.

METHODS

In this phase 3, randomised, double-blind trial, we recruited eligible patients with histologically confirmed oestrogen receptor-positive or progesterone receptor-positive, or both, locally advanced or metastatic breast cancer from 113 academic hospitals and community centres in 20 countries. Eligible patients were endocrine therapy-naive, with WHO performance status 0-2, and at least one measurable or non-measurable lesion. Patients were randomly assigned (1:1) to fulvestrant (500 mg intramuscular injection; on days 0, 14, 28, then every 28 days thereafter) or anastrozole (1 mg orally daily) using a computer-generated randomisation scheme. The primary endpoint was progression-free survival, determined by Response Evaluation Criteria in Solid Tumors version 1·1, intervention by surgery or radiotherapy because of disease deterioration, or death from any cause, assessed in the intention-to-treat population. Safety outcomes were assessed in all patients who received at least one dose of randomised treatment (including placebo). This trial is registered with ClinicalTrials.gov, number NCT01602380.

FINDINGS

Between Oct 17, 2012, and July 11, 2014, 524 patients were enrolled to this study. Of these, 462 patients were randomised (230 to receive fulvestrant and 232 to receive anastrozole). Progression-free survival was significantly longer in the fulvestrant group than in the anastrozole group (hazard ratio [HR] 0·797, 95% CI 0·637-0·999, p=0·0486). Median progression-free survival was 16·6 months (95% CI 13·83-20·99) in the fulvestrant group versus 13·8 months (11·99-16·59) in the anastrozole group. The most common adverse events were arthralgia (38 [17%] in the fulvestrant group vs 24 [10%] in the anastrozole group) and hot flushes (26 [11%] in the fulvestrant group vs 24 [10%] in the anastrozole group). 16 (7%) of 228 patients in in the fulvestrant group and 11 (5%) of 232 patients in the anastrozole group discontinued because of adverse events.

INTERPRETATION

Fulvestrant has superior efficacy and is a preferred treatment option for patients with hormone receptor-positive locally advanced or metastatic breast cancer who have not received previous endocrine therapy compared with a third-generation aromatase inhibitor, a standard of care for first-line treatment of these patients.

FUNDING

AstraZeneca.

Randomized phase II trial of fulvestrant alone or in combination with bortezomib in hormone receptor-positive metastatic breast cancer resistant to aromatase inhibitors: a New York Cancer Consortium trial

The proteasome inhibitor bortezomib enhances the effect of the selective estrogen receptor (ER) downregulator (SERD) fulvestrant by causing accumulation of cytoplasmic ER aggregates in preclinical models. The purpose of this trial was to determine whether bortezomib enhanced the effectiveness of fulvestrant. One hundred eighteen postmenopausal women with ER-positive metastatic breast cancer resistant to aromatase inhibitors (AIs) were randomized to fulvestrant alone (Arm A-500 mg intramuscular (i.m.) day -14, 1, 15 in cycle 1, and day 1 of additional cycles) or in combination with bortezomib (Arm B-1.6 mg/m² intravenous (i.v.) on days 1, 8, 15 of each cycle). The study was powered to show an improvement in median progression-free survival (PFS) from 5.4 to 9.0 months and compare PFS rates at 6 and 12 months (α=0.10, β=0.10). Patients with progression on fulvestrant could cross over to the combination (arm C). Although there was no difference in median PFS (2.7 months in both arms), the hazard ratio for PFS in Arm B versus Arm A (referent) was 0.73 (95% confidence interval (CI)=0.49, 1.09, P=0.06, 1-sided log-rank test, significant at the prespecified 1-sided 0.10 α level). At 12 months, the PFS proportion in Arm A and Arm B was 13.6% and 28.1% (P=0.03, 1-sided χ²-test; 95% CI for difference (14.5%)=-0.06, 29.1%). Of 27 patients on arm A who crossed over to the combination (arm C), 5 (18%) were progression-free for at least 24 weeks. Bortezomib likely enhances the effectiveness of fulvestrant in AI-resistant, ER-positive metastatic breast cancer by reducing acquired resistance, supporting additional evaluation of proteasome inhibitors in combination with SERDs.

Mechanism of drug resistance in relation to site of metastasis: Meta-analyses of randomized controlled trials in advanced breast cancer according to anticancer strategy

BACKGROUND

Breast cancer is heterogeneous at different levels: biologic subtypes, intratumoral areas, and sites of metastases. Randomized controlled trials (RCTs) classify metastatic sites as visceral or non-visceral, but this has little influence in treatment decisions, particularly in the absence of clinical urgency. Indeed, it is unclear if response to treatments differs among sites of metastases.

PATIENTS AND METHODS

RCTs investigating 3 different anticancer strategies in metastatic breast cancer were identified: (1) new hormonal therapy, (2) new targeted therapies in hormone receptor positive tumours (everolimus or palbociclib), and (3) new anti-HER2 therapies. RCTs reporting hazard ratios (HR) for Progression Free Survival (PFS) and Overall Survival (OS) for sub-groups based on sites of metastases were weighted using generic inverse variance approach, and pooled in meta-analyses using Revman 5.3. Subgroup difference was tested with Chi² statistics.

RESULTS

Eleven RCTs (6701pts.) qualified. There was a significant difference in PFS between women with visceral versus non-visceral metastases when two endocrine strategies were compared, with benefits limited to women with visceral metastases [Pooled HR 0.85; 95% CI, 0.77-0.95 versus 1.02 (0.88-1.18) for non-visceral; p(difference)=0.05]. However, combination of an endocrine therapy and a targeted therapy was associated with better PFS compared to endocrine therapy alone for both groups [HR 0.51 (0.43-0.60) versus 0.45 (0.36-0.56) for non-visceral; p(difference)=0. 36]. Novel HER-2 targeted therapies were associated with significantly better PFS and OS only in visceral metastases [HR 0.59 (0.52-0.66) versus 0.71(0.44-1.13) for non-visceral, p(difference)=0.45, for PFS; and 0.64 (0.56-0.73) versus 0.82 (0.57=1.19) for non-visceral, p(difference)=0.20, for OS].

CONCLUSION

Combination of targeted agents and endocrine therapy results in concordant, superior PFS suggesting targetable endocrine resistance across metastatic sites. Discordant responses with endocrine strategy alone support use of targeted therapy, rather than change in endocrine agent at disease progression. HER2 targeted therapies may be less effective in areas of poor vascularization.