Landscape of Baseline and Acquired Genomic Alterations in Circulating Tumor DNA with Abemaciclib Alone or with Endocrine Therapy in Advanced Breast Cancer

PURPOSE

To identify potential predictors of response and resistance mechanisms in patients with hormone receptor-positive (HR+), HER2-negative (HER2-) advanced breast cancer (ABC) treated with the cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor abemaciclib ± endocrine therapy (ET), baseline and acquired genomic alterations in circulating tumor DNA (ctDNA) were analyzed and associated with clinical outcomes.

EXPERIMENTAL DESIGN

MONARCH 3: postmenopausal women with HR+, HER2- ABC and no prior systemic therapy in the advanced setting were randomly assigned to abemaciclib or placebo plus nonsteroidal aromatase inhibitor (NSAI). nextMONARCH: women with HR+, HER2- metastatic breast cancer that progressed on/after prior ET and chemotherapy were randomly assigned to abemaciclib alone (two doses) or plus tamoxifen. Baseline and end-of-treatment plasma samples from patients in MONARCH 3 and nextMONARCH (monotherapy arms) were analyzed to identify somatic genomic alterations. Association between genomic alterations and median progression-free survival (mPFS) was assessed.

RESULTS

Most patients had ≥1 genomic alteration detected in baseline ctDNA. In MONARCH 3, abemaciclib+NSAI was associated with improved mPFS versus placebo+NSAI, regardless of baseline alterations. ESR1 alterations were less frequently acquired in the abemaciclib+NSAI arm than placebo+NSAI. Acquired alterations potentially associated with resistance to abemaciclib ± NSAI included RB1 and MYC.

CONCLUSIONS

In MONARCH 3, certain baseline ctDNA genomic alterations were prognostic for ET but not predictive of abemaciclib response. Further studies are warranted to assess whether ctDNA alterations acquired during abemaciclib treatment differ from other CDK4/6 inhibitors. Findings are hypothesis generating; further exploration is warranted into mechanisms of resistance to abemaciclib and ET. See related commentary by Wander and Bardia, p. 2008.

Brazilian breast cancer patient-reported outcomes: What really matters for these women

Introduction

Patient-Reported Outcomes (PRO) are directly reported by the patient without interpretation of the patient's response by a clinician or anyone else and pertains to the patient's health, quality of life, or functional status associated with health care or treatment. It can provide patients’ perspectives regarding treatment benefit and harm beyond survival and are often the outcomes of most importance to patients. This study aims to describe and analyze outcomes reported by Brazilian women diagnosed with breast cancer and rank the most important attributes for these patients.

Methods

Observational descriptive study composed of exploratory interviews followed by online questionnaires applied to a convenience sample of women diagnosed with breast cancer.

Results

Twelve women were interviewed to explore the main outcomes and preferences about their treatments, such as the most common side effects and the most impacted aspects of life after diagnosis and BC treatment. Psychological, emotional, and sexual impacts were frequently described as impacted aspects. Fifty-three women, from all the five Brazilian regions, answered the online questionnaire. Following an order of importance ranking, the following outcomes were chosen, respectively: overall survival, progression-free survival; and quality of life. The treatment effects that were considered less important, among this sample, were pain and adverse events.

Conclusions

Thinking about expanding the therapeutic quality of users, it is essential to take into account the experiences of patients. PRO is a trend in current research to achieve this goal, in order to influence the decisions of HTA agencies about the importance of valuing outcomes that affect patients' lives.

Genomic Markers of CDK 4/6 Inhibitor Resistance in Hormone Receptor Positive Metastatic Breast Cancer

Cyclin-dependent kinase 4/6 inhibitors are the standard of care for hormone receptor-positive metastatic breast cancer. This retrospective study reports on genomic biomarkers of CDK 4/6i resistance utilizing genomic data acquired through routine clinical practice. Patients with HR+ MBC treated with palbociclib, ribociclib, or abemaciclib and antiestrogen therapy were identified. Patients were grouped into early (<6 months); intermediate (6−24 months for 0−1 lines; 6−9 months for ≥2 lines); or late progressors (>24 months for 0−1 lines; >9 months PFS for ≥2 lines). NGS and RNA sequencing data were analyzed in association with PFS, and survival analysis was stratified by prior lines of chemotherapy. A total of 795 patients with HR+ MBC treated with CDK 4/6i were identified. Of these, 144 (18%) patients had genomic data and 29 (3.6%) had RNA data. Among the 109 patients who received CDK4/6i as 1st- or 2nd-line therapy, 17 genes showed associations with PFS (p-value ≤ 0.15 and HR ≥ 1.5 or HR < 0.5). Whole transcriptome RNAseq was analyzed for 24/109 (22%) patients with 0−1 prior lines of therapy and 56 genes associated with PFS (HR ≥ 4 or HR ≤ 0.25 and FDR ≤ 0.15). In this retrospective analysis, genomic biomarkers including FGFR1 amplification, PTEN loss, and DNA repair pathway gene mutations showed significant associations with shorter PFS for patients receiving CDK4/6 inhibitor therapy.

β‑catenin blockers enhance the effect of CDK4/6 inhibitors on stemness and proliferation suppression in endocrine‑resistant breast cancer cells

Wnt/β‑catenin signaling is involved in endocrine resistance and stem cell‑like properties of hormone receptor‑positive breast cancer cells. Palbociclib is a well‑known inhibitor of cyclin‑dependent kinase 4 and 6 (CDK4/6 inhibitor) that downregulates the activation of retinoblastoma protein, thereby inhibiting the cell cycle in breast cancer cells. The inhibitory effects of a combination of palbociclib and ICG‑001, a β‑catenin small‑molecule inhibitor, were investigated in tamoxifen‑resistant breast cancer cell lines. Tamoxifen‑resistant MCF‑7 (TamR) cells were established by continuously exposing MCF‑7 cells to tamoxifen. The characteristics associated with the stem cell‑like property of cancer were assessed using western blotting, cell cycle analysis, and the mammosphere assay. The effects of the combination of palbociclib and ICG‑001 were evaluated in control MCF‑7 and TamR cell lines. Compared with control cells, TamR cells exhibited elevated levels of Nanog, Sox2, ALDH1, and p‑STAT3, indicating stem cell‑like characteristics, and elevated β‑catenin activity. TamR cells also showed significantly higher mammosphere‑forming efficiency. Several markers of stem cell‑like nature of TamR cells showed reduced levels upon treatment of cells with the drug combination; there was a greater reduction in the levels of these markers when the cells were treated with the combination than in the case where cells were treated with one of the drugs individually (combination index value for 25 µM palbociclib and 50 µM ICG‑001 was 1.1±0.02). TamR cells treated with the palbociclib and ICG‑001 combination demonstrated significantly reduced cell proliferation and mammosphere‑forming efficiency compared with the cells treated with one of these drugs. The combination of the drugs could additively inhibit proliferation and suppress stem cell‑like characteristics. These results suggest that β‑catenin plays a role in endocrine‑resistant breast cancer; the inhibition of β‑catenin and CDK4/6 together can overcome endocrine resistance in breast cancer cells.

Patient preferences for breast cancer treatments: a discrete choice experiment in France, Ireland, Poland, Spain

Aim: To understand breast cancer patients' trade-offs when choosing treatments and to identify the most important treatment attributes which drive decisions. Materials & methods: A discrete choice experiment was conducted in France, Ireland, Poland and Spain. Progression-free survival, febrile neutropenia, pain, functional well-being and out-of-pocket payment were the treatment attributes. Results: 371 patients were willing to pay €6896 per year for 1 additional year of progression-free survival, €17,288 per year for perfect functional well-being and €15,138 for one pain-free year. Patients are willing to trade off progression-free survival months for better functional abilities and less pain. Conclusion: Patient preferences should be considered by regulatory agencies, reimbursement bodies, payors and clinicians for best treatment choices for the individuals.

Baseline lymphopenia as prognostic factor in patients with metastatic breast cancer treated with palbociclib

Cyclin-dependent-kinase 4-6 inhibitors (CDK4/6i) have improved the management of hormone receptor (HR)⁺/human epidermal growth factor receptor (HER)2^- metastatic breast cancer (mBC). Currently, there are no valid prognostic factors for response to CDK4/6i. Baseline lymphopenia is reported as a prognostic factor in several types of cancer. The present retrospective study aimed to evaluate the effect of baseline absolute lymphocyte count (ALC) on response to palbociclib. Progression-free survival (PFS) was the primary endpoint. Secondary endpoints were overall survival (OS), best response and safety. A total of 114 patients treated for mBC between 2016 and 2019 were included. Median baseline ALC was 1.4 g/l (range, 0.2-4.3 g/l). A total of 65 (57%) and 49 (43%) patients had baseline ALC values of <1.5 and ≥1.5 g/l, respectively. Patients with baseline lymphopenia exhibited significantly shorter PFS (6 vs. 10 months; P=0.004) and OS (20 vs. 33 months; P=0.02). ALC <1.5 g/l independently predicted worse survival, as indicated by multivariate analysis (P=0.04; hazard ratio, 1.76; 95% confidence interval, 1.02-3.02). Patients with baseline ALC <1.5 g/l had significantly less partial response (14 vs. 22%; P=0.016) and more disease progression (46 vs. 20%; P=0.016) than those with ALC ≥1.5 g/l. ALC is a strong and easy-to-use dosage with prognostic factor for patients with HR⁺/HER2^- mBC treated with palbociclib and endocrine therapy. Lymphopenia may also be a predictive factor of early progression. These data need to be verified in a larger prospective study.

A mixed-methods study of cyclin-dependent kinase 4 and 6 inhibitor symptom burden and quality of life among metastatic breast cancer patients and providers

Background

Cyclin‐dependent kinase 4 and 6 (CDK4/6) inhibitor targeted therapies dramatically improve survival outcomes for metastatic breast cancer (MBC), but they are associated with significant symptom burden that can impact patients’ health‐related quality of life (HRQOL) and treatment outcomes. This study is the first to describe CDK4/6 inhibitor symptoms from the lived perspectives of MBC patients taking CDK4/6 inhibitors and healthcare providers involved in MBC care. This study also explored patients’ symptom management and HRQOL concerns, and gathered feedback about developing supportive interventions for MBC.

Methods

MBC patients taking CDK4/6 inhibitors (N = 20) and MBC healthcare providers (N = 12) participated in semi‐structured interviews that were analyzed for qualitative themes. MBC patients completed surveys about HRQOL, symptoms, and unmet needs.

Results

Patient and provider perceptions of CDK4/6 inhibitor symptoms did not align with patients perceiving symptoms as more burdensome. Patients reported that supportive resources (e.g., support groups, blogs) that are not specific to MBC do not adequately meet their needs. Patients and providers were enthusiastic about developing supportive interventions specifically for MBC and offered considerations for designing such interventions.

Conclusions

Findings highlight differences in perceptions of CDK4/6 inhibitor symptom burden between MBC patients and providers. Results will inform the development of supportive interventions to assist MBC patients in managing CDK4/6 inhibitor symptom burden and maintaining HRQOL. Such interventions could also improve treatment outcomes.

Metastatic breast cancer (MBC) patient and provider perceptions of symptoms associated with CDK4/6 inhibitor did not align, with patients perceiving symptoms as more burdensome. Patients reported that supportive resources (e.g., support groups, blogs) that are not specific to MBC do not adequately meet their needs, however patients and providers were enthusiastic about developing supportive interventions specifically for MBC and offered considerations for designing such interventions. Results will inform the development of supportive interventions to assist MBC patients in managing CDK4/6 inhibitor symptom burden and maintaining health‐related quality of life.

Ribociclib-Induced Pneumonitis: A Case Report

BACKGROUND

Cyclin-dependent kinase 4/6 (CDK 4/6) inhibitors have been a significant breakthrough in the management of hormone receptor-positive, HER2-negative metastatic breast cancer based on the results of several large phase III randomized trials. The most common reported toxicity is myelosuppression due to disease such as leukopenia, neutropenia, and thrombocytopenia. Other toxicities associated with CDK 4/6 inhibitors include mucositis, fatigue, gastrointestinal side effects, hepatic toxicities, and QTc prolongation. Despite a good toxicity profile in pivotal studies, the increased rates of use in clinical practice may show less prevalent but lethal toxicity such as lung injury.

CASE PRESENTATION

Here, we describe a female patient with metastatic hormone receptor-positive/human epidermal growth factor 2-negative breast cancer who developed lung toxicity while on ribociclib.

DISCUSSION

Lung injury is a possible side effect of CDK 4/6 inhibitors and there is an increasing need to understand the management of this side effect.

Combined CDK2 and CDK4/6 Inhibition Overcomes Palbociclib Resistance in Breast Cancer by Enhancing Senescence

Breast cancer represents the number one global cancer burden in women and the hormone receptor (HR)-positive subtype comprises approximately 70% of breast cancers. Unfortunately, acquired resistance ultimately occurs in almost all cases, even though cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors are a highly effective therapy for HR-positive/human epidermal growth factor receptor 2-negative subtype. Here, we investigated mechanisms of resistance to CDK4/6 inhibitor and potential therapeutic strategies using our palbociclib-resistant preclinical model. We observed that cyclin E was significantly overexpressed in palbociclib-resistant cells, and similar association was also confirmed in pleural effusion samples collected from HR-positive breast cancer patients. After confirmation of cyclin E-CDK2 interaction by co-immunoprecipitation, we demonstrated CDK2 inhibition combined with palbociclib synergistically suppressed proliferation of palbociclib-resistant cells and growth of palbociclib-resistant xenograft in mice. We also proved that enhancing C-MYC-mediated senescence is a novel mechanism behind the synergism created by targeting both CDK2 and CDK4/6. Furthermore, the clinical relevance of cyclin E as a therapeutic target was supported by significant association between CCNE1 overexpression and poor prognosis based on large-scale public gene expression data sets in HR-positive breast cancer patients. Therefore, we propose cyclin E-CDK2 signaling as a promising therapeutic target for overcoming cyclin E-associated resistance to CDK4/6 inhibitor.

The Influence of Cancer Molecular Subtypes and Treatment on the Mutation Spectrum in Metastatic Breast Cancers

Next-generation sequencing has sparked the exploration of cancer genomes, with the aim of discovering the genetic etiology of the disease and proposing rationally designed therapeutic interventions. Driver gene alterations have been comprehensively charted, but the improvement of cancer patient management somewhat lags behind these basic breakthroughs. Recently, large-scale sequencing that focused on metastasis, the main cause of cancer-related deaths, has shed new light on the driving forces at work during disease progression, particularly in breast cancer. Despite a fairly stable pool of driver genetic alterations between early and late disease, a number of therapeutically targetable mutations have been found enriched in metastatic samples. The molecular processes fueling disease progression have been delineated in recent studies and the clonal composition of breast cancer samples can be examined in detail. Here we discuss how these findings may be combined to improve the diagnosis of breast cancer to better select patients at risk, and to identify targeted agents to treat advanced diseases and to design therapeutic strategies exploiting vulnerabilities of cancer cells rooted in their ability to evolve and drive disease progression.

Palbociclib and ribociclib in breast cancer: consensus workshop on the management of concomitant medication

Drug–drug interactions are of significant concern in clinical practice in oncology, particularly in patients receiving Cyclin-dependent kinase (CDK) 4/6 inhibitors, which are typically exposed to long-term regimens. This article presents the highlights from the ‘First Workshop on Pharmacology and Management of CDK4/6 Inhibitors: Consensus about Concomitant Medications’. The article is structured into two modules. The educational module includes background information regarding drug metabolism, corrected QT (QTc) interval abnormalities, management of psychotropic drugs and a comprehensive review of selected adverse effects of palbociclib and ribociclib. The collaborative module presents the conclusions of the five working groups, each of which comprised five experts from different fields. From these conclusions positive lists of drugs for treating common comorbid conditions that can be safely administered concomitantly with palbociclib and/or ribociclib were developed.

Fulvestrant-Based Combination Therapy for Second-Line Treatment of Hormone Receptor-Positive Advanced Breast Cancer

Fulvestrant is recommended for patients with hormone receptor-positive (HR+) advanced breast cancer (ABC) who progress after aromatase inhibitor therapy. As most patients in this setting have already developed mechanisms of resistance to endocrine therapy, targeting biological pathways associated with endocrine resistance in combination with fulvestrant may improve outcomes. Therefore, evidence supporting a combinatorial treatment approach in the second-line setting was investigated based on a search of PubMed and ClinicalTrials.gov . Twenty-eight studies of targeted therapies plus fulvestrant as second-line treatment for HR+ ABC were identified, including three and six key randomized trials exploring cyclin-dependent kinase 4/6 (CDK4/6) inhibitors and phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibitors plus fulvestrant respectively. Additional combinations with fulvestrant included inhibitors of epidermal growth factor receptors, androgen receptor, and the bromodomain and extra-terminal family of proteins. Across the studies reviewed with available data, the addition of targeted therapies to fulvestrant resulted in clinically meaningful improvements in progression-free survival compared with fulvestrant alone. While some challenging toxicities were observed, most adverse events could be effectively managed. Selection of second-line targeted therapy for use with fulvestrant should consider prior treatment as well as the mutation status of the tumor. In conclusion, available data indicate that fulvestrant combined with agents targeting mechanisms of endocrine resistance is a promising approach. The ongoing trials identified in this review will help further inform the selection of combination treatments with fulvestrant for HR+ ABC.

Why upfront use of CDK inhibitors for the treatment of advanced breast cancer may be wasteful, and how we can increase their value

Three Cyclin Dependent Kinase 4/6 (CDK) inhibitors have been approved by the United Stated Food and Drug Administration for front line treatment of advanced hormone receptor positive breast cancer based on improvements in progression free survival against endocrine monotherapy. Two clinical trials have so far reported results on overall survival but both are negative. CDK inhibitors are usually tolerated well but they do add to inconvenience and cost - for example, grade III-IV neutropenia occur at a frequency of over 60% requiring frequent blood work at least during the initial months of treatment. These drugs cost over $ 13,500 for a 4-week cycle in the United States, and are responsible for billions of dollars annually in drug cost alone. Importantly, many women with metastatic breast cancer do well for a long time with endocrine therapy alone and CDK inhibitors do not have a predictive marker. Selective use of these agents in later lines may improve substantially the convenience and cost without compromise in overall outcome. However, with results demonstrating impressive improvements in PFS published in major medical journals coupled with patients' natural desire for "best available" options, the trend among oncologists is to prescribe these drugs as the default front-line treatment. In this commentary I caution readers against over interpretation of results from the CDK inhibitor trials, describe adverse consequences of routine front-line use, and explain why selective use in later line may yield a higher value.

ASCO 2018 highlights: metastatic breast cancer

This article reviews the clinically most relevant presentations at the American Society of Clinical Oncology (ASCO) annual meeting 2018 on the topic of metastatic breast cancer. In the randomized placebo-controlled phase 3 trial MONALEESA-3, testing ribociclib vs. placebo in combination with fulvestrant in postmenopausal women or men with hormone receptor-positive (HR+) and HER2-negative (HER2−) advanced breast cancer (ABC), an increase of median progression-free survival (PFS) from 12.8 months to 20.5 months by the addition of the CDK4/6 inhibitor was reported (HR 0.59; P > 0.01). Taselisib, an alpha specific PI3K inhibitor, was tested in combination with fulvestrant in pretreated HR+/HER2− ABC patients with PIK3CA mutations in the placebo-controlled phase 3 trial SANDPIPER. PFS was significantly longer (7.4 months vs 5.4 months; HR 0.70, P < 0.01) but severe adverse events were more frequent (32% and 9%) in the taselisib group. In triple-negative breast cancer, the AKT inhibitor capivasertib (AZD5363) was combined with paclitaxel as first-line treatment in the placebo-controlled phase 2 trial PAKT. In patients with altered PIK3CA, AKT1 or PTEN, median PFS increased from 3.7 months to 9.3 months (HR 0.30; two-sided P = 0.01). No treatment effect was shown in the non-altered group. The most common adverse events attributed to capivasertib were diarrhea, fatigue and stomatitis. Results of two phase I trials of trastuzumab antibody-drug conjugates (ADCs) indicated HER2 as a non-oncogenic surface target in breast cancer patients expressing HER2.

Hormone receptor positive, HER2 negative metastatic breast cancer: Impact of CDK4/6 inhibitors on the current treatment paradigm

Resistance to endocrine therapy is a significant therapeutic challenge in the treatment of women with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer. Cyclin-dependent kinase (CDK)4/6 inhibitors in combination with endocrine therapy have been shown to improve progression free survival, overall response rate and clinical benefit rate in women with HR+ HER2- metastatic breast cancer compared with endocrine therapy alone. This review examines the clinical evidence to support the use of CDK4/6 inhibitors in first and second line settings. Practical guidance is provided for the use of CDK4/6 inhibitors, including tolerability data, monitoring requirements and management of key toxicities for each of the available agents.