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

Proteomic profiling reveals that ESR1 mutations enhance cyclin-dependent kinase signaling

Three quarters of all breast cancers express the estrogen receptor (ER, ESR1 gene), which promotes tumor growth and constitutes a direct target for endocrine therapies. ESR1 mutations have been implicated in therapy resistance in metastatic breast cancer, in particular to aromatase inhibitors. ESR1 mutations promote constitutive ER activity and affect other signaling pathways, allowing cancer cells to proliferate by employing mechanisms within and without direct regulation by the ER. Although subjected to extensive genetic and transcriptomic analyses, understanding of protein alterations remains poorly investigated. Towards this, we employed an integrated mass spectrometry based proteomic approach to profile the protein and phosphoprotein differences in breast cancer cell lines expressing the frequent Y537N and Y537S ER mutations. Global proteome analysis revealed enrichment of mitotic and immune signaling pathways in ER mutant cells, while phosphoprotein analysis evidenced enriched activity of proliferation associated kinases, in particular CDKs and mTOR. Integration of protein expression and phosphorylation data revealed pathway-dependent discrepancies (motility vs proliferation) that were observed at varying degrees across mutant and wt ER cells. Additionally, protein expression and phosphorylation patterns, while under different regulation, still recapitulated the estrogen-independent phenotype of ER mutant cells. Our study is the first proteome-centric characterization of ESR1 mutant models, out of which we confirm estrogen independence of ER mutants and reveal the enrichment of immune signaling pathways at the proteomic level.

A network meta-analysis of efficacy and safety for first-line and second/further-line therapies in postmenopausal women with hormone receptor-positive, HER2-negative, advanced breast cancer

BACKGROUND

Hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR + /HER2 -) advanced breast cancer is a prevalent subtype among postmenopausal women. Despite the growing number of randomized clinical trials (RCTs) exploring this topic, the efficacy and safety of first-line and second/further-line treatments remain uncertain. Accordingly, our aim was to conduct a comprehensive evaluation of the efficacy and safety of these therapies through network meta-analysis.

METHODS

RCTs were identified by searching Pubmed, Embase, and major cancer conferences. The efficacy of interventions was assessed using the hazard ratios (HRs) of progression-free survival (PFS) and overall survival (OS), while safety was indicated by the incidence of any grade adverse events (AEs), grade 3-5 AEs, AEs leading to treatment discontinuation, and AEs leading to death. Both time-variant HRs fractional polynomial models and time-invariant HRs Cox-proportional hazards models were considered for handling time-to-event data. Safety indicators were analyzed using Bayesian network meta-analysis. Additionally, subgroup analyses were conducted based on patient characteristics.

RESULTS

A total of 41 RCTs (first-line 17, second/further-lines 27) were included in the analysis. For first-line treatment, the addition of Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors to endocrine therapy significantly improved therapeutic efficacy in terms of both PFS and OS, demonstrating the best performance across all mechanisms. Specifically, the combination of Abemaciclib and Letrozole demonstrated the most favorable performance in terms of PFS, while Ribociclib plus Fulvestrant yielded the best outcomes in OS. Incorporating the immune checkpoint inhibitor Avelumab into the regimen with CDK4/6 inhibitors and selective estrogen receptor degraders significantly enhanced both PFS and OS in second-line or later treatments. Regarding safety, endocrine monotherapy performed well. Regarding safety, endocrine monotherapy performed well. There is mounting evidence suggesting that most CDK4/6 inhibitors may demonstrate poorer performance with respect to hematologic AEs. However, additional evidence is required to further substantiate these findings.

CONCLUSIONS

CDK4/6 inhibitors, combined with endocrine therapy, are pivotal in first-line treatment due to their superior efficacy and manageable AEs. For second/further-line treatment, adding immune checkpoint inhibitors to CDK4/6 inhibitors plus endocrine therapy may produce promising results. However, to reduce the results' uncertainty, further trials comparing these novel treatments are warranted.

TRIAL REGISTRATION

Registration number: PROSPERO (CRD42022377431).

Single-cell morphological and transcriptome analysis unveil inhibitors of polyploid giant breast cancer cells in vitro

Considerable evidence suggests that breast cancer therapeutic resistance and relapse can be driven by polyploid giant cancer cells (PGCCs). The number of PGCCs increases with the stages of disease and therapeutic stress. Given the importance of PGCCs, it remains challenging to eradicate them. To discover effective anti-PGCC compounds, there is an unmet need to rapidly distinguish compounds that kill non-PGCCs, PGCCs, or both. Here, we establish a single-cell morphological analysis pipeline with a high throughput and great precision to characterize dynamics of individual cells. In this manner, we screen a library to identify promising compounds that inhibit all cancer cells or only PGCCs (e.g., regulators of HDAC, proteasome, and ferroptosis). Additionally, we perform scRNA-Seq to reveal altered cell cycle, metabolism, and ferroptosis sensitivity in breast PGCCs. The combination of single-cell morphological and molecular investigation reveals promising anti-PGCC strategies for breast cancer treatment and other malignancies.

The ubiquitin-proteasome system in breast cancer

Ubiquitin-proteasome system (UPS) is a selective proteolytic system that is associated with the expression or function of target proteins and participates in various physiological and pathological processes of breast cancer. Inhibitors targeting the 26S proteasome in combination with other drugs have shown promising therapeutic effects in the clinical treatment of breast cancer. Moreover, several inhibitors/stimulators targeting other UPS components are also effective in preclinical studies, but have not yet been applied in the clinical treatment of breast cancer. Therefore, it is vital to comprehensively understand the functions of ubiquitination in breast cancer and to identify potential tumor promoters or tumor suppressors among UPS family members, with the aim of developing more effective and specific inhibitors/stimulators targeting specific components of this system.

Repurposing FDA-approved drugs as inhibitors of therapy-induced invadopodia activity in glioblastoma cells

Glioblastoma (GBM) is the most prevalent primary central nervous system tumour in adults. The lethality of GBM lies in its highly invasive, infiltrative, and neurologically destructive nature resulting in treatment failure, tumour recurrence and death. Even with current standard of care treatment with surgery, radiotherapy and chemotherapy, surviving tumour cells invade throughout the brain. We have previously shown that this invasive phenotype is facilitated by actin-rich, membrane-based structures known as invadopodia. The formation and matrix degrading activity of invadopodia is enhanced in GBM cells that survive treatment. Drug repurposing provides a means of identifying new therapeutic applications for existing drugs without the need for discovery or development and the associated time for clinical implementation. We investigate several FDA-approved agents for their ability to act as both cytotoxic agents in reducing cell viability and as 'anti-invadopodia' agents in GBM cell lines. Based on their cytotoxicity profile, three agents were selected, bortezomib, everolimus and fludarabine, to test their effect on GBM cell invasion. All three drugs reduced radiation/temozolomide-induced invadopodia activity, in addition to reducing GBM cell viability. These drugs demonstrate efficacious properties warranting further investigation with the potential to be implemented as part of the treatment regime for GBM.

Molecular characterization of ESR1 variants in breast cancer

PURPOSE

Estrogen receptor 1 (ESR1) mutations and fusions typically arise in patients with hormone receptor-positive breast cancer after aromatase inhibitor therapy, whereby ESR1 is constitutively activated in a ligand-independent manner. These variants can impact treatment response. Herein, we characterize ESR1 variants among molecularly profiled advanced breast cancers.

METHODS

DNA next-generation sequencing (592-gene panel) data from 9860 breast cancer samples were retrospectively reviewed. Gene fusions were detected using the ArcherDx fusion assay or whole transcriptome sequencing (n = 344 and n = 4305, respectively). Statistical analyses included Chi-square and Fisher's exact tests.

RESULTS

An ESR1 ligand-binding domain (LBD) mutation was detected in 8.6% of tumors evaluated and a pathogenic ESR1 fusion was detected in 1.6%. Most ESR1 LBD mutations/fusions were from estrogen receptor (ER)-positive samples (20.1% and 4.9%, respectively). The most common ESR1 LBD mutations included D538G (3.3%), Y537S (2.3%), and E380Q (1.1%) mutations. Among biopsy sites, ESR1 LBD mutations were most observed in liver metastases. Pathogenic ESR1 fusions were identified in 76 samples (1.6%) with 40 unique fusion partners. Evaluating co-alterations, ESR1 variant (mutation/fusion) samples more frequently expressed androgen receptor (78.0% vs 58.6, P < 0.0001) and less frequently immune checkpoint proteins than ESR1 wild-type (PD-1 20.0% vs 53.4, P < 0.05; immune cell PD-L1 10.0% vs 30.2, P < 0.0001).

CONCLUSION

We have described one of the largest series of ESR1 fusions reported. ESR1 LBD mutations were commonly identified in ER-positive disease. Limited data exists regarding the clinical impact of ESR1 fusions, which could be an area for future therapeutic exploration.

ESR1 fusions and therapeutic resistance in metastatic breast cancer

Breast cancer is the most frequent female malignant tumor, and the leading cause of cancer death in women worldwide. The most common subtype of breast cancer is hormone receptor positive that expresses the estrogen receptor (ER). Targeting ER with endocrine therapy (ET) is the current standard of care for ER positive (ER+) breast cancer, reducing mortality by up to 40% in early- stage disease. However, resistance to ET represents a major clinical challenge for ER+ breast cancer patients leading to disease recurrence or progression of metastatic disease. Salient drivers of ET resistance are missense mutations in the ER gene (ESR1) leading to constitutive transcriptional activity and reduced ET sensitivity. These mutations are particularly prominent and deleterious in metastatic breast cancer (MBC). In addition to activating ESR1 point mutations, emerging evidence imposes that chromosomal translocation involving the ESR1 gene can also drive ET resistance through the formation of chimeric transcription factors with constitutive transcriptional activity. Although these ESR1 gene fusions are relatively rare, they are enriched in ET resistant metastatic disease. This review discusses the characteristics of ER fusion proteins and their association with clinical outcomes in more aggressive and metastatic breast cancer. The structure and classification of ER fusion proteins based on function and clinical significance are also addressed. Finally, this review summarizes the metastatic phenotypes exhibited by the ER fusion proteins and their role in intrinsic ET resistance.

Phase Ib Study of the Oral Proteasome Inhibitor Ixazomib (MLN9708) and Fulvestrant in Advanced ER+ Breast Cancer Progressing on Fulvestrant

LESSONS LEARNED

Fulvestrant is a selective estrogen receptor (ER)-downregulating antiestrogen that blocks ER transcriptional activity and is approved for ER-positive breast cancer. Fulvestrant also induces accumulation of insoluble ER and activates an unfolded protein response; proteasome inhibitors have been shown to enhance these effects in preclinical models.

BACKGROUND

Fulvestrant is a selective estrogen receptor (ER)-downregulating antiestrogen that blocks ER transcriptional activity and is approved for ER-positive (+) breast cancer. Fulvestrant also induces accumulation of insoluble ER and activates an unfolded protein response; proteasome inhibitors have been shown to enhance these effects in preclinical models.

METHODS

This is a single-center phase Ib study with a 3+3 design of fulvestrant and the proteasome inhibitor ixazomib (MLN9708) in patients with advanced ER+ breast cancer that was progressing on fulvestrant. A dose-escalation design allowed establishment of the ixazomib maximum tolerated dose (MTD). Secondary objectives included progression-free survival, pharmacokinetics, and tumor molecular analyses.

RESULTS

Among nine evaluable subjects, treatment was well-tolerated without dose-limiting toxicities The MTD of ixazomib was 4 mg in combination with fulvestrant. Plasma concentrations of the active form of ixazomib (MLN2238) in the 4-mg dose cohort had a median (range) maximal concentration (Cmax ) of 155 (122-171) ng/mL, time of maximal concentration (Tmax ) of 1 (1-1.5) hour, terminal elimination half-life of 66.6 (57.3-102.6) hour after initial dose, and area under the curve (AUC) of 5,025 (4,160-5,345) ng*h/mL. One partial response was observed, and median progression-free survival was 51 days (range, 47-137).

CONCLUSION

This drug combination has a favorable safety profile and antitumor activity in patients with fulvestrant-resistant advanced ER+ breast cancer that justifies future testing.

Evaluation of the contribution of randomised cancer clinical trials evaluating agents without documented single-agent activity

BACKGROUND

With the development of targeted agents, the approach to combination cancer therapy has evolved to focus on identifying ways in which pathway inhibition by one agent may enhance the activity of other agents. In theory, this implies that under this new paradigm, agents are no longer required to show single-agent activity, as the pathway inhibited by the targeted agent may only have a therapeutic effect when given with other agents. This raises the question of the extent to which anticancer agents without single-agent activity can contribute to effective combination regimens.

PATIENTS AND METHODS

We reviewed outcomes of randomised phase 2 combination trials sponsored by the National Cancer Institute Cancer Therapy Evaluation Program that were activated in 2008 to 2017 and noted the single-agent activity of the experimental agents.

RESULTS

Fifty-three trials were identified, and 50 had available results: 7 (14%), 15 (30%) and 28 (56%) had experimental agents with single-agent activity classified as active, inactive and indeterminate, respectively. Thirteen per cent (95% CI=1.7% to 40.5%) of trials evaluating inactive agents and 11.6% (95% CI=3.9% to 25.1%) of trials evaluating agents without known single-agent activity (pooled inactive and indeterminate) were positive, compared with 42.9% (95% CI=9.9% to 81.6%) for agents with single-agent activity.

CONCLUSIONS

Incorporating agents without documented single-agent activity into treatment regimens is unlikely to produce meaningful improvements in activity unless there is compelling biological rationale. This finding has important implications for the prioritisation of anticancer agents for combination testing, and for the allocation of clinical trial resources.

Endocrine Resistance in Breast Cancer: The Role of Estrogen Receptor Stability

Therapy of hormone receptor positive breast cancer (BCa) generally targets estrogen receptor (ER) function and signaling by reducing estrogen production or by blocking its interaction with the ER. Despite good long-term responses, resistance to treatment remains a significant issue, with approximately 40% of BCa patients developing resistance to ET. Mutations in the gene encoding ERα, ESR1, have been identified in BCa patients and are implicated as drivers of resistance and disease recurrence. Understanding the molecular consequences of these mutations on ER protein levels and its activity, which is tightly regulated, is vital. ER activity is in part controlled via its short protein half-life and therefore changes to its stability, either through mutations or alterations in pathways involved in protein stability, may play a role in therapy resistance. Understanding these connections and how ESR1 alterations could affect protein stability may identify novel biomarkers of resistance. This review explores the current reported data regarding posttranslational modifications (PTMs) of the ER and the potential impact of known resistance associated ESR1 mutations on ER regulation by affecting these PTMs in the context of ET resistance.

Designing historical control studies with survival endpoints using exact statistical inference

Historical control trials compare an experimental treatment with a previously conducted control treatment. By assigning all recruited samples to the experimental arm, historical control trials can better identify promising treatments in early phase trials compared with randomized control trials. Existing designs of historical control trials with survival endpoints are based on asymptotic normal distribution. However, it remains unclear whether the asymptotic distribution of the test statistic is close enough to the true distribution given relatively small sample sizes in early phase trials. In this article, we address this question by introducing an exact design approach for exponentially distributed survival endpoints, and compare it with an asymptotic design in both real examples and simulation examples. Simulation results show that the asymptotic test could lead to bias in the sample size estimation. We conclude the proposed exact design should be used in the design of historical control trials.

Endocrine therapy-based treatments in hormone receptor-positive/HER2-negative advanced breast cancer: systematic review and network meta-analysis

BACKGROUND

Several endocrine therapy (ET)-based treatments are available for patients with advanced breast cancer. We assessed the efficacy of different ET-based treatments in patients with hormone receptor-positive/HER2-negative advanced breast cancer with endocrine-sensitive or endocrine-resistant disease.

METHODS

We searched Medline and Cochrane Central Register of Controlled Trials up to 15 October 2019 and abstracts from major conferences from 2016 to October 2019. We included phase II/III randomised trials, comparing ≥2 ET-based treatments. Progression-free survival (PFS) and overall survival (OS) were analysed by network meta-analyses using MTC Bayesian models based on both fixed-effect and random-effect models; relative treatment effects were measured as HRs and 95% credibility intervals (CrI). All statistical tests were two-sided. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed and this systematic review is registered in the PROSPERO database.

RESULTS

55 publications reporting on 32 trials (n=12 293 patients) were included. Regarding PFS in the endocrine sensitive setting (n=5200; 12 trials), the combination of cyclin-dependent kinases (CDK)4/6-inhibitors (CDK4/6i)+fulvestrant 500 mg (F500) was likely the most effective treatment (surface under the cumulative ranking curve (SUCRA)=97.3%), followed by CDK4/6i+aromatase inhibitor ±goserelin; there was no significant difference between them (HR 0.82; 95% CrI 0.54-1.25). Regarding OS (n=2157; five trials), the most effective treatment was probably CDK4/6i+F500 (SUCRA=97.3%); comparing CDK4/6i+F500 versus F500 held a HR of 0.77 (95% CrI 0.63-0.95). Regarding PFS in the endocrine-resistant setting (n=6635; 20 trials), CDK4/6i+F500 was likely the most effective treatment (SUCRA=95.7%), followed by capivasertib+F500, without significant difference between them (HR 0.91; 95% CrI 0.60-1.36). For OS (n=4377; 11 trials), the most effective treatments were capivasertib+F500 (SUCRA=84.7%) and CDK4/6i+F500 (SUCRA=69.9%). Comparing CDK4/6i+F500 versus F500 held a HR of 0.77 (95% CrI 0.67-0.89).

CONCLUSIONS

CDK4/6i+F500 is likely the best treatment option in both endocrine-sensitive and endocrine-resistant diseases for PFS, and in endocrine-sensitive patients for OS. Concerning OS in endocrine-resistant patients, capivasertib+F500 and CDK4/6i+F500 are likely the best treatments.

PROSPERO REGISTRATION NUMBER

CRD42018104628.

Endocrine therapy resistance: new insights

The estrogen receptor positive (ER+) subset is the dominant contributor to global deaths from breast cancer which now exceeds 500,000 deaths annually. Lethality is driven by endocrine resistance, which has been shown to be associated with high mutational rates and extreme subclonal diversity. Treatment forces subclonal selection until the patient eventually succumbs to metastatic treatment-resistant disease. Recently, we have been addressing several questions related to this process: What is the cause of the increased mutation rate in lethal ER+ breast cancer? Why is endocrine therapy resistance related to mutational load? What are the functions of the somatic mutations that are eventually selected in the treatment resistant and metastatic clones? These questions have provoked new mechanistic hypotheses that link resistance to endocrine agents to: (1) Specific defects in single strand break repair are associated with increased mortality from ER+ breast cancer [1,2]; (2) Loss/mutations of certain single strand break repair proteins that disrupt estrogen-regulated cell cycle control through the ATM, CHK2, CDK4 axis [1,2] thereby directly coupling endocrine therapy resistance to specific DNA repair defects; (3) Acquired mutations that drive metastasis include the generation of in-frame ESR1 gene fusions that activate epithelial-to-mesenchymal transition (EMT) driven metastasis as well as endocrine drug-resistant proliferation [3].

Combination Immunotherapy Strategies in Breast Cancer

Purpose of Review

We summarize combination immunotherapy strategies for the treatment of breast cancer, with a focus on metastatic disease. First, a general overview of combination approaches is presented according to breast cancer subtype. Second, additional review of promising combination approaches is presented.

Recent Findings

Combination strategies utilizing chemotherapy or radiotherapy with immune checkpoint inhibition are being evaluated across multiple phase III trials. Dual immunotherapy strategies, such as dual immune checkpoint inhibition or combined co-stimulation/co-inhibition, have supportive preclinical evidence and are under early clinical investigation. Modulation of the immune microenvironment via cytokines and vaccination strategies, as well as locally focused treatments to enhance antigenic responses, are active areas of research.

Summary

Pre-clinical and translational research sheds new light on numerous ways the immune system may be modulated to fight against cancer. We describe current and emerging combination approaches which may improve patient outcomes in metastatic breast cancer.

Endocrine and Targeted Therapy for Hormone-Receptor-Positive, HER2-Negative Advanced Breast Cancer: Insights to Sequencing Treatment and Overcoming Resistance Based on Clinical Trials

Background: Advanced hormone-receptor positive HER2 negative breast cancer is a common and a very heterogeneous disease. Hormone therapy is the main first line treatment of choice, given alone or in combination with other agents that have shown to improve patient outcomes, Nevertheless, treatment remains generally palliative rather than curative. Sequencing of such treatment remains challenging, especially with resurgence of variable resistance patterns. Multiple attempts have been made to overcome resistance and improve patient survival, yet resistance remains not very well understood and metastatic cancer remains a disease with dismal prognosis.

Methods: In this paper, we searched pubmed database as well as local and international meetings for all studies discussing advanced and metastatic hormone-receptor-positive, her2-negative breast cancer, hormonal treatment, resistance to hormonal treatment, mechanism of resistance, and means to overcome such resistance.

Conclusion: There does not exist an optimal treatment sequence for hormone-receptor-positive, her2-negative advanced breast cancer. However, after review of literature, a reasonable approach may be starting with tamoxifen, aromatase inhibitors, or fulvestrant in absence of visceral crisis, in addition to ensuring adequate ovarian function suppression in pre/peri-menopausal women. Aromatase inhibitors and fulvestrant seem to be superior. Resistance to such agents is increasing, mostly attributed to genetic and molecular changes. Multiple modalities are addressed to overcome such resistance including use of CKD4/6 inhibitors, mTOR inhibitors and PI3K inhibitors in addition to other agents under study, all with promising results. CDK4/6 inhibitors work best when used in frontline setting. Finally, treatment of breast cancer remains a growing field, and more studies are to be awaited.

ESR1 alterations and metastasis in estrogen receptor positive breast cancer

Endocrine therapy is essential for the treatment of patients with estrogen receptor positive (ER+) breast cancer, however, resistance and the development of metastatic disease is common. Understanding how ER+ breast cancer metastasizes is critical since the major cause of death in breast cancer is metastasis to distant organs. Results from many studies suggest dysregulation of the estrogen receptor alpha gene (ESR1 ) contributes to therapeutic resistance and metastatic biology. This review covers both pre-clinical and clinical evidence on the spectrum of ESR1 alterations including amplification, point mutations, and genomic rearrangement events driving treatment resistance and metastatic potential of ER+ breast cancer. Importantly, we describe how these ESR1 alterations may provide therapeutic opportunities to improve outcomes in patients with lethal, metastatic breast cancer.

A comparison of fulvestrant plus a targeted agent with fulvestrant alone in hormone receptor-positive advanced breast cancer that progressed on prior endocrine therapy: a meta-analysis

Fulvestrant is recommended for the hormone receptor-positive metastatic breast cancer (MBC) patients progressed during or after prior endocrine therapy. Notably, recent evidence has also demonstrated that adding a targeted agent to fulvestrant conferred a significantly clinical benefit in these patients. Since these results were inconsistent among the studies, this meta-analysis herein was conducted to compare the efficacy and toxicities of the fulvestrant-based combination therapy with fulvestrant monotherapy. Thus, a systemic research was performed in PubMed, Embase, and Cochrane library to identify relevant Phase II or Phase III randomized controlled trials. The progression-free survival (PFS), overall response rate (ORR), and toxicities were evaluated. And HR, risk ratio (RR), and their 95% CIs were employed to complete the pooled analyses. In total, 13 studies with 3,910-hour positive MBC patients progressed on prior endocrine therapy were included in our meta-analysis. Improvements of doublet-agents group were proven in terms of PFS (HR 0.73, 95% CI =0.63–0.86, P=0.000) and ORR (RR 2.07, 95% CI =1.67–2.58, P=0.000). And the further subgroup analysis also demonstrated that fulvestrant in combination with a cyclin-dependent kinase (CDK4/6) inhibitor or a PI3K/mTOR inhibitor was associated with a superior efficacy (RR 2.72, 95% CI =1.93–3.83, P=0.000 and RR 1.60, 95% CI =1.15–2.23, P=0.005, respectively). However, the efficacy was comparable between the other combination strategies and fulvestrant alone. With respect to the adverse effects, adding a targeted agent to fulvestrant also produced more frequent grade 3/4 toxicities (RR 3.86, 95% CI =2.66–5.61, P=0.000). Taken together, combination of fulvestrant with a targeted agent, especially inhibitors targeting CDK4/6 or PI3K/mTOR pathway, may open a new avenue for more effective therapies in relapse or metastatic hormone receptor-positive breast cancer after prior aromatase inhibitors or tamoxifen treatment. In addition, identifying reliable biomarkers to delineate which subgroup of patients will specially benefit from fulvestrant-based combination therapy is warranted.

Comparative efficacy of different targeted therapies plus fulvestrant for advanced breast cancer following progression on prior endocrine therapy: a network meta-analysis

Background

We performed a network meta-analysis of randomized controlled trials (RCTs) to indirectly compare the efficacy of different targeted agents with fulvestrant for patients with hormone-receptor-positive (HR+) and human epidermal growth factor receptor type 2-negative (HER2-) advanced breast cancer (ABC) following progression on prior endocrine therapy.

Methods

The titles/abstracts were searched from the PubMed, EMBASE, and the Cochrane Library databases for RCTs to evaluate the efficacy of palbociclib plus fulvestrant vs alternative targeted therapies plus fulvestrant for postmenopausal HR+/HER2- ABC following progression on prior endocrine therapy. In addition, the primary measured outcome was progression-free survival (PFS) and objective response rate. The surface under the cumulative ranking (SUCRA) value of each treatment was calculated to achieve the best ranking for each treatment.

Results

A total of 11 studies, including 4,178 patients in the network meta-analysis, were included and analyzed. In terms of the pooled hazard ratios (HRs) for PFS, palbociclib plus fulvestrant was superior to other target agents plus fulvestrant (HR=0.62, 95% credible interval [CrI]: 0.40-0.96; HR=0.62, 95% CrI: 0.47-0.96; for pictilisib plus fulvestrant and buparlisib plus fulvestrant, respectively). Ribociclib plus fulvestrant has no difference in abemaciclib plus fulvestrant and palbociclib plus fulvestrant (HR =1.02, 95% CrI =0.72-1.45; HR =1.22, 95% CrI =0.84-1.78). In terms of objective response rate, compared with placebo plus fulvestrant, abemaciclib plus fulvestrant, dovitinib plus fulvestrant, buparlisib plus fulvestrant, and palbociclib plus fulvestrant had a significant difference (odds ratio [OR] =2.84, 95% CrI =1.91- 4.31; OR =3.62, 95% CrI =1.21-12.48; OR =1.80, 95% CrI =1.25-2.60; and OR =2.52, 95% CrI =1.43- 4.72, respectively).

Conclusion

According to the present study, palbociclib plus fulvestrant may be the optimal treatment for HR+/HER2- postmenopausal women with ABC after disease progression following endocrine therapy.

The efficacy and safety of targeted therapy plus fulvestrant in postmenopausal women with hormone-receptor positive advanced breast cancer: A meta-analysis of randomized-control trials

OBJECTIVE

To evaluate the efficacy and safety of targeted therapy plus fulvestrant for postmenopausal patients with hormone receptor-positive advanced breast cancer.

METHODS

Pubmed, Embase and Web of Science databases were systematically searched on February 26, 2018. Eligible studies were screened according to selection criteria, and two reviewers independently extracted outcome data which included progression-free survival, overall survival, objective response rate, clinical benefit rate and toxicities. RevMan 5.3 and STATA 11.0 software were used to conduct meta-analysis.

RESULTS

Thirteen articles including twelve randomized-control trials fulfilled selection criteria. There was no evidence regarding the existence of publication bias and high-risk bias of quality in the selected studies. In previously endocrine therapy-treated postmenopausal patients with hormone-receptor positive advanced breast cancer, the PFS (HR = 0.77, 95%CI: 0.66-0.91) and ORR (RR = 1.78, 95%CI: 1.35-2.34) of combination therapy group were significantly higher than that from fulvestrant monotherapy group. Besides, a statistically significant difference in PFS was found across the two arms in postmenopausal women with PIK3CA-mutant ctDNA tumor (HR = 0.52, 95% CI: 0.39-0.69). Moreover, the risk of adverse events (RR = 1.09, 95%CI: 1.05-1.13), CTCAE≥3 (RR = 1.97, 95%CI: 1.49-2.60) and discontinuation due to adverse events (RR = 4.91, 95%CI: 3.37-7.15) were also significantly different between two treatment groups. Sensitivity analysis showed PLOMA-3 trial was an important factor of heterogeneity.

DISCUSSION

Even though the combination of targeted therapy plus fulvestrant improved PFS and increased ORR in advanced breast cancer patients, the toxicities of combination therapy were also higher than fulvestrant monotherapy. Further studies related to inhibitors targeting the specific signaling pathway or receptors are urgently needed, and more efforts concerning precision medicine of targeted therapy plus endocrine therapy should be taken to improve the clinical benefits.

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.

The iron chelator deferasirox synergises with chemotherapy to treat triple-negative breast cancers

To ensure their high proliferation rate, tumor cells have an iron metabolic disorder causing them to have increased iron needs, making them more susceptible to iron deprivation. This vulnerability could be a therapeutic target. In breast cancers, the development of new therapeutic approaches is urgently needed for patients with triple-negative tumors, which frequently relapse after chemotherapy and suffer from a lack of targeted therapies. In this study, we demonstrated that deferasirox (DFX) synergises with standard chemotherapeutic agents such as doxorubicin, cisplatin and carboplatin to inhibit cell proliferation and induce apoptosis and autophagy in triple-negative breast cancer (TNBC) cells. Moreover, the combination of DFX with doxorubicin and cyclophosphamide delayed recurrences in breast cancer patient-derived xenografts without increasing the side-effects of chemotherapies alone or altering the global iron storage of mice. Antitumor synergy of DFX and doxorubicin seems to involve downregulation of the phosphoinositide 3-kinase and nuclear factor-κB pathways. Iron deprivation in combination with chemotherapy could thus help to improve the effectiveness of chemotherapy in TNBC patients without increasing toxicity. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Differential prioritization of therapies to subtypes of triple negative breast cancer using a systems medicine method

Triple negative breast cancer (TNBC) is a group of cancers whose heterogeneity and shortage of effective drug therapies has prompted efforts to divide these cancers into molecular subtypes. Our computational platform, entitled GenEx-TNBC, applies concepts in systems biology and polypharmacology to prioritize thousands of approved and experimental drugs for therapeutic potential against each molecular subtype of TNBC. Using patient-based and cell line-based gene expression data, we constructed networks to describe the biological perturbation associated with each TNBC subtype at multiple levels of biological action. These networks were analyzed for statistical coincidence with drug action networks stemming from known drug-protein targets, while accounting for the direction of disease modulation for coinciding entities. GenEx-TNBC successfully designated drugs, and drug classes, that were previously shown to be broadly effective or subtype-specific against TNBC, as well as novel agents. We further performed biological validation of the platform by testing the relative sensitivities of three cell lines, representing three distinct TNBC subtypes, to several small molecules according to the degree of predicted biological coincidence with each subtype. GenEx-TNBC is the first computational platform to associate drugs to diseases based on inverse relationships with multi-scale disease mechanisms mapped from global gene expression of a disease. This method may be useful for directing current efforts in preclinical drug development surrounding TNBC, and may offer insights into the targetable mechanisms of each TNBC subtype.

Proteasome inhibitors prevent bi-directional HER2/estrogen-receptor cross-talk leading to cell death in endocrine and lapatinib-resistant HER2+/ER+ breast cancer cells

Amplification and/or overexpression of the human epidermal growth factor 2 (HER2) oncogene occurs in about 13–15% of invasive breast cancer and triggers breast cancer cell proliferation, survival and metastatic progression. Around half of all breast cancers with HER2 overexpression co-express hormone receptors (HR) such as those for estrogen and progesterone. Aberrant signaling through HER2 and other members of the HER-family mediates endocrine-resistance in estrogen receptor alpha (ERα) positive breast cancer. On the other hand, ERα co-expression has been shown to attenuate the efficiency of anti-HER2 therapies. These findings indicate that HER2 and ERα synergize to escape from both anti-ERα and anti-HER2-targeted therapies. Rationally designed clinical trials that combine endocrine therapy with anti-HER2 agents to interfere with HER2/ERα cross-talk have been conducted. However, the outcome of these trials suggests that novel therapeutic approaches are needed to further improve inhibition of HER2 and other HER-family members in conjunction with a more efficient ERα blockade. Here, we demonstrate that carfilzomib and bortezomib stabilize the HER2-specific protein tyrosine phosphatase BDP1 leading to decreased HER2 autophosphorylation, reduced HER2 activity and subsequently attenuated activation of the PI3K/Akt-pathway, together with blockade of ERα expression. We further observed that proteasome inhibitors (PIs) reverse autophosphorylation and thereby inhibit the activity of constitutively active mutant HER2. We also demonstrate that PIs cause cell death in lapatinib and endocrine-resistant HER2+/ER+ breast cancer cells. These findings suggest that PIs might have the potential to improve the management of HER2+/ER+ breast cancer patients by efficiently disrupting the bi-directional HER2/ERα cross-talk.

Novel Strategies to Improve the Endocrine Therapy of Breast Cancer

Endocrine therapy (ET) constitutes the usual first-line of therapy for patients in the treatment of metastatic hormone receptor-positive breast cancer. Unfortunately, not all patients respond to first-line endocrine treatment due to intrinsic resistance, while others may initially respond but eventually progress with secondary acquired resistance leading to disease progression. Mechanisms of resistance to anti-estrogen therapy include, loss of expression for estrogen or progesterone receptor, upregulation of epidermal receptor growth factor 2, increased receptor tyrosine kinase signaling, leading to activation of various intracellular pathways that are involved in signal transduction such as PI3K/AKT/mammalian target of rapamycin, and others. Growing understanding of the signal cascade of estrogen receptors and the signaling pathways that interact with estrogen receptors has revealed the complex role of these receptors in cell growth and proliferation, and on the mechanism in development of resistance. These insights have led to the development of targeted therapies that may prove to be effective options for the treatment of breast cancer and may overcome hormone therapy resistance. In this review we summarize some of the mechanisms of endocrine resistance, selected clinical trials of ET and targeted therapies, which might interfere with estrogen receptor pathways and might reduce or reverse resistance to traditional, sequential, single-agent ET.

Updates from the 2014 San antonio breast cancer symposium

The san antonio breast cancer syposium (SABCS 2014) was an exciting one this year. Data from the SOFT trial was presented that had potential implications on the treatment of pre menapausal women with hormone receptor positive breast cancer. In a phase II trial fulvestrant was found to significantly improve progression free and overall survival compared to anastrazole in the first line treatment of women with hormone receptor positive metastatic breast cancer. We saw a number of intersting abstracts looking at trying to refine the role of platinums and exploring the role of blocking PD-1 among women with triple receptor negative breast cancer. We also saw the results of a number of trials trying to refine standard chemotherapeutic regimens. Here we will review some fon the most interesting abstracts presented this year at SABCS 2014.