Palbociclib in combination with endocrine therapy versus capecitabine in hormonal receptor-positive, human epidermal growth factor 2-negative, aromatase inhibitor-resistant metastatic breast cancer: a phase III randomised controlled trial-PEARL

BACKGROUND

Palbociclib plus endocrine therapy (ET) is the standard treatment of hormone receptor-positive and human epidermal growth factor receptor 2-negative, metastatic breast cancer (MBC). However, its efficacy has not been compared with that of chemotherapy in a phase III trial.

PATIENTS AND METHODS

PEARL is a multicentre, phase III randomised study in which patients with aromatase inhibitor (AI)-resistant MBC were included in two consecutive cohorts. In cohort 1, patients were randomised 1 : 1 to palbociclib plus exemestane or capecitabine. On discovering new evidence about estrogen receptor-1 (ESR1) mutations inducing resistance to AIs, the trial was amended to include cohort 2, in which patients were randomised 1 : 1 between palbociclib plus fulvestrant and capecitabine. The stratification criteria were disease site, prior sensitivity to ET, prior chemotherapy for MBC, and country of origin. Co-primary endpoints were progression-free survival (PFS) in cohort 2 and in wild-type ESR1 patients (cohort 1 + cohort 2). ESR1 hotspot mutations were analysed in baseline circulating tumour DNA.

RESULTS

From March 2014 to July 2018, 296 and 305 patients were included in cohort 1 and cohort 2, respectively. Palbociclib plus ET was not superior to capecitabine in both cohort 2 [median PFS: 7.5 versus 10.0 months; adjusted hazard ratio (aHR): 1.13; 95% confidence interval (CI): 0.85-1.50] and wild-type ESR1 patients (median PFS: 8.0 versus 10.6 months; aHR: 1.11; 95% CI: 0.87-1.41). The most frequent grade 3-4 toxicities with palbociclib plus exemestane, palbociclib plus fulvestrant and capecitabine, respectively, were neutropenia (57.4%, 55.7% and 5.5%), hand/foot syndrome (0%, 0% and 23.5%), and diarrhoea (1.3%, 1.3% and 7.6%). Palbociclib plus ET offered better quality of life (aHR for time to deterioration of global health status: 0.67; 95% CI: 0.53-0.85).

CONCLUSIONS

There was no statistical superiority of palbociclib plus ET over capecitabine with respect to PFS in MBC patients resistant to AIs. Palbociclib plus ET showed a better safety profile and improved quality of life.

ESR1 Mutations and Overall Survival on Fulvestrant versus Exemestane in Advanced Hormone Receptor-Positive Breast Cancer: A Combined Analysis of the Phase III SoFEA and EFECT Trials

PURPOSE

ESR1 mutations are acquired frequently in hormone receptor-positive metastatic breast cancer after prior aromatase inhibitors. We assessed the clinical utility of baseline ESR1 circulating tumor DNA (ctDNA) analysis in the two phase III randomized trials of fulvestrant versus exemestane.

EXPERIMENTAL DESIGN

The phase III EFECT and SoFEA trials randomized patients with hormone receptor-positive metastatic breast cancer who had progressed on prior nonsteroidal aromatase inhibitor therapy, between fulvestrant 250 mg and exemestane. Baseline serum samples from 227 patients in EFECT, and baseline plasma from 161 patients in SoFEA, were analyzed for ESR1 mutations by digital PCR. The primary objectives were to assess the impact of ESR1 mutation status on progression-free (PFS) and overall survival (OS) in a combined analysis of both studies.

RESULTS

ESR1 mutations were detected in 30% (151/383) baseline samples. In patients with ESR1 mutation detected, PFS was 2.4 months [95% confidence interval (CI), 2.0-2.6] on exemestane and 3.9 months (95% CI, 3.0-6.0) on fulvestrant [hazard ratio (HR), 0.59; 95% CI, 0.39-0.89; P = 0.01). In patients without ESR1 mutations detected, PFS was 4.8 months (95% CI, 3.7-6.2) on exemestane and 4.1 months (95% CI, 3.6-5.5) on fulvestrant (HR, 1.05; 95% CI, 0.81-1.37; P = 0.69). There was an interaction between ESR1 mutation and treatment (P = 0.02). Patients with ESR1 mutation detected had 1-year OS of 62% (95% CI, 45%-75%) on exemestane and 80% (95% CI, 68%-87%) on fulvestrant (P = 0.04; restricted mean survival analysis). Patients without ESR1 mutations detected had 1-year OS of 79% (95% CI, 71%-85%) on exemestane and 81% (95% CI, 74%-87%) on fulvestrant (P = 0.69).

CONCLUSIONS

Detection of ESR1 mutations in baseline ctDNA is associated with inferior PFS and OS in patients treated with exemestane versus fulvestrant.

Combined Inhibition of STAT3 and DNA Repair in Palbociclib-Resistant ER-Positive Breast Cancer

PURPOSE

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors are currently used in combination with endocrine therapy to treat advanced hormone receptor-positive, HER2-negative breast cancer. Although this treatment doubles time to progression compared with endocrine therapy alone, about 25%-35% of patients do not respond, and almost all patients eventually acquire resistance. Discerning the mechanisms of resistance to CDK4/6 inhibition is crucial in devising alternative treatment strategies.

EXPERIMENTAL DESIGN

Palbociclib-resistant cells (MCF-7 and T47D) were generated in a step-wise dose-escalading fashion. Whole-exome sequencing, genome-wide expression analysis, and proteomic analysis were performed in both resistant and parental (sensitive) cells. Pathway alteration was assessed mechanistically and pharmacologically. Biomarkers of altered pathways were examined in tumor samples from patients with palbociclib-treated breast cancer whose disease progressed while on treatment.

RESULTS

Palbociclib-resistant cells are cross-resistant to other CDK4/6 inhibitors and are also resistant to endocrine therapy (estrogen receptor downregulation). IL6/STAT3 pathway is induced, whereas DNA repair and estrogen receptor pathways are downregulated in the resistant cells. Combined inhibition of STAT3 and PARP significantly increased cell death in the resistant cells. Matched tumor samples from patients with breast cancer who progressed on palbociclib were examined for deregulation of estrogen receptor, DNA repair, and IL6/STAT3 signaling, and results revealed that these pathways are all altered as compared with the pretreatment tumor samples.

CONCLUSIONS

Palbociclib resistance induces endocrine resistance, estrogen receptor downregulation, and alteration of IL6/STAT3 and DNA damage response pathways in cell lines and patient samples. Targeting IL6/STAT3 activity and DNA repair deficiency using a specific STAT3 inhibitor combined with a PARP inhibitor could effectively treat acquired resistance to palbociclib.

Complexity of genome sequencing and reporting: Next generation sequencing (NGS) technologies and implementation of precision medicine in real life

The finalization of the Human Genome Project in 2003 paved the way for a deeper understanding of cancer, favouring a faster progression towards "personalized" medicine. Research in oncology has progressively focused on the sequencing of cancer genomes, to better understand the genetic basis of tumorigenesis and identify actionable alterations to guide cancer therapy. Thanks to the development of next-generation-sequencing (NGS) techniques, sequencing of tumoral DNA is today technically easier, faster and cheaper. Commercially available NGS panels enable the detection of single or global genomic alterations, namely gene mutation and mutagenic burden, both on germline and somatic DNA, potentially predicting the response or resistance to cancer treatments. Profiling of tumor DNA is nowadays a standard in cancer research and treatment. In this review we discuss the history, techniques and applications of NGS in cancer care, under a "personalized tailored therapy" perspective.

Low-Molecular-Weight Cyclin E in Human Cancer: Cellular Consequences and Opportunities for Targeted Therapies

Cyclin E, a regulatory subunit of cyclin-dependent kinase 2 (CDK2), is central to the initiation of DNA replication at the G1/S checkpoint. Tight temporal control of cyclin E is essential to the coordination of cell-cycle processes and the maintenance of genome integrity. Overexpression of cyclin E in human tumors was first observed in the 1990s and led to the identification of oncogenic roles for deregulated cyclin E in experimental models. A decade later, low-molecular-weight cyclin E (LMW-E) isoforms were observed in aggressive tumor subtypes. Compared with full-length cyclin E, LMW-E hyperactivates CDK2 through increased complex stability and resistance to the endogenous inhibitors p21CIP1 and p27KIP1 LMW-E is predominantly generated by neutrophil elastase-mediated proteolytic cleavage, which eliminates the N-terminal cyclin E nuclear localization signal and promotes cyclin E's accumulation in the cytoplasm. Compared with full-length cyclin E, the aberrant localization and unique stereochemistry of LMW-E dramatically alters the substrate specificity and selectivity of CDK2, increasing tumorigenicity in experimental models. Cytoplasmic LMW-E, which can be assessed by IHC, is prognostic of poor survival and predicts resistance to standard therapies in patients with cancer. These patients may benefit from therapeutic modalities targeting the altered biochemistry of LMW-E or its associated vulnerabilities. Cancer Res; 78(19); 5481-91. ©2018 AACR.

Circulating tumor DNA (ctDNA) in the era of personalized cancer therapy

The heterogeneity of tumor is considered as a major difficulty to victorious personalized cancer medicine. There is an extremeneed of consistent response evaluation for in vivo tumor heterogeneity anditscoupledconflict mechanisms. In this occasion researchers will be able to keep pace withpredictive, preventive, personalized, and Participatory (P4) medicine for cancer managements. In fact tumor heterogeneity is a central part of cancer evolution,soin order to progress in understanding of the dynamics within a tumor some diagnostic apparatus should be improved. Latest molecular techniques like Next generation Sequencing (NGS) and ultra-deep sequencing could disclose some clones within a liquid tumor biopsy which mainly responsible of treatment resistance. Circulating tumor DNA (ctDNA) as a main component of liquid biopsy is agifted biomarker for cancer mutation tracking as well as profiling. Personalized medicine facilitate learning regarding to genetic pools of tumor and their possible respond to treatment which could be much easier by using of ctDNA.With this information, cliniciansarelooking forward to find the best strategies for prevention, screening, and treatment in the way of precision medicine. Currently, numerous clinical efficacy of such informative improved treatment are in hand. Here we represent the review of plasma-derived ctDNA studies use in personalized cancer managements.

Advances in Endocrine Therapy for Postmenopausal Metastatic Breast Cancer

A majority of breast cancers are hormone receptor (HR) positive and are responsive to various types of hormone manipulation. Endocrine therapy is the preferred first-line therapy for patients with advanced estrogen receptor (ER) positive, HER2-negative breast cancer who do not have symptomatic visceral disease. Endocrine therapy is often continued in the second- and third-line setting, with chemotherapy deferred until tumor becomes endocrine therapy refractory and/or a visceral crisis in imminent. Therapeutic options vary based on clinical presentation and include single-agent therapies such as tamoxifen, aromatase inhibitors and fulvestrant, and combination therapies options. Over the past few years, multiple trials have shown significant improvement in outcomes when endocrine therapy is combined with CDK 4/6 inhibitors or mTOR inhibitors. Improved efficacy comes at a cost of a modest increase in toxicity. Mechanisms of ER resistance have been defined leading to multiple strategies to improve efficacy and overcome resistance. These include the combination therapies options mentioned above and other novel drugs that are in development. This review will summarize the existing literature regarding endocrine therapy in postmenopausal metastatic breast cancer and outline treatment approaches in the first-line metastatic setting and beyond.

Safety of everolimus plus exemestane in patients with hormone-receptor-positive, HER2-negative locally advanced or metastatic breast cancer: results of phase IIIb BALLET trial in Spain

BACKGROUND

Everolimus with exemestane has shown promising activity in patients with hormone-receptor (HR)-positive HER2-negative endocrine-resistant advanced breast cancer. It is necessary, therefore, to characterize the safety profile of this new combination in the real-world clinical setting and in the broadest possible population.

PATIENTS AND METHODS

Post-menopausal women with HR-positive HER2-negative advanced breast cancer progressing after prior non-steroidal aromatase inhibitors (NSAIs) were included. The objectives of this analysis were to evaluate the safety profile of this combination in a subset of Spanish patients in the BALLET trial and to characterize grade 3 and 4 adverse events (AEs) in routine clinical practice in Spain.

RESULTS

Between September 2012 and July 2013, 429 patients (20% of the overall study population) were included in the BALLET study in 52 hospitals in Spain, of whom 100 (23%) were ≥ 70 years. The median treatment duration was 3.14 and 3.03 months for exemestane and everolimus, respectively. The most common reasons for discontinuation of treatment were local reimbursement of everolimus (43%), followed by disease progression (31%) and the incidence of AEs (15%). The most frequent AEs causing permanent discontinuation were pneumonitis (4%), asthenia (2%) and stomatitis (2%). Overall, 87% of patients experienced at least one AE of any grade, 30% of patients at least one grade 3 AE and 2% of patients a grade 4 AE.

CONCLUSION

The safety profile in Spanish patients of the BALLET trial is consistent with the results obtained in the overall population of the trial, as well as in previous clinical trials.

Frequent Genetic Aberrations in the CDK4 Pathway in Acral Melanoma Indicate the Potential for CDK4/6 Inhibitors in Targeted Therapy

Purpose: Effective therapies for the majority of metastatic acral melanoma patients have not been established. Thus, we investigated genetic aberrations of CDK4 pathway in acral melanoma and evaluated the efficacy of CDK4/6 inhibitors in targeted therapy of acral melanoma.Experimental Design: A total of 514 primary acral melanoma samples were examined for the copy number variations (CNV) of CDK4 pathway-related genes, including Cdk4, Ccnd1, and P16^INK4a , by QuantiGenePlex DNA Assay. The sensitivity of established acral melanoma cell lines and patient-derived xenograft (PDX) containing typical CDK4 aberrations to CDK4/6 inhibitors was evaluated.Results: Among the 514 samples, 203 cases, 137 cases, and 310 cases, respectively, showed Cdk4 gain (39.5%), Ccnd1 gain (26.7%), and P16^INK4a loss (60.3%). The overall frequency of acral melanomas that contain at least one aberration in Cdk4, Ccnd1, and P16^INK4a was 82.7%. The median overall survival time for acral melanoma patients with concurrent Cdk4 gain with P16^INK4a loss was significantly shorter than that for patients without such aberrations (P = 0.005). The pan-CDK inhibitor AT7519 and selective CDK4/6 inhibitor PD0332991 could inhibit the cell viability of acral melanoma cells and the tumor growth of PDX with Cdk4 gain plus Ccnd1 gain, Cdk4 gain plus P16^INK4a loss, and Ccnd1 gain plus P16^INK4a loss.Conclusions: Genetic aberration of CDK4 pathway is a frequent event in acral melanoma. Acral melanoma cell lines and PDX containing CDK4 pathway aberrations are sensitive to CDK4/6 inhibitors. Our study provides evidence for the testing of CDK4/6 inhibitors in acral melanoma patients. Clin Cancer Res; 23(22); 6946-57. ©2017 AACR.

CDK4/6 and autophagy inhibitors synergistically induce senescence in Rb positive cytoplasmic cyclin E negative cancers

Deregulation of the cell cycle machinery is a hallmark of cancer. While CDK4/6 inhibitors are FDA approved (palbociclib) for treating advanced estrogen receptor-positive breast cancer, two major clinical challenges remain: (i) adverse events leading to therapy discontinuation and (ii) lack of reliable biomarkers. Here we report that breast cancer cells activate autophagy in response to palbociclib, and that the combination of autophagy and CDK4/6 inhibitors induces irreversible growth inhibition and senescence in vitro, and diminishes growth of cell line and patient-derived xenograft tumours in vivo. Furthermore, intact G1/S transition (Rb-positive and low-molecular-weight isoform of cyclin E (cytoplasmic)-negative) is a reliable prognostic biomarker in ER positive breast cancer patients, and predictive of preclinical sensitivity to this drug combination. Inhibition of CDK4/6 and autophagy is also synergistic in other solid cancers with an intact G1/S checkpoint, providing a novel and promising biomarker-driven combination therapeutic strategy to treat breast and other solid tumours.

CDK4/6-Cyclin D pathway is often deregulated in cancer; therefore specific inhibitors have been developed. Here the authors show that treatment with CDK4/6 inhibitors activate autophagy in breast cancer cells; thus, combination of such inhibitors with autophagy inhibitors results in a synergistic effect on tumour growth.

ASCO 2016: highlights in breast cancer

At the 2016 ASCO Annual Meeting, several pertinent studies in the field of breast cancer were presented. MA17.R was the first randomized phase III trial to evaluate the prolongation of adjuvant aromatase-inhibitor (AI) therapy from 5 to 10 years; while a significant reduction of disease-free survival events was observed in the extended treatment group, the absolute difference was relatively small and longer endocrine therapy resulted in a higher fracture rate. A combined analysis of three North American trials emphasized the superiority of anthracycline containing adjuvant chemotherapy regimens compared with docetaxel/cyclophosphamide (TC), while the PANTHER trial investigated dose-dense tailored adjuvant treatment. In metastatic breast cancer, the main interest was on cyclin-dependent kinase (CDK) 4/6 inhibitors. In PALOMA-2, the addition of palbociclib to letrozole prolonged progression-free survival (PFS) from 14.5 to 24.8 months resulting in the longest PFS data ever reported in the first-line setting. A subgroup analysis of premenopausal patients accrued to PALOMA-3 indicated that in this patient subset, ovarian function suppression plus fulvestrant and palbociclib yielded results comparable to the postmenopausal population. ESR1 mutations were another focus of interest as these activating mutations in the gene coding for the estrogen receptor alpha apparently evolve under the selection pressure of AI therapy.