Cyclin-Dependent Kinase 4/6 Inhibitors as Neoadjuvant Therapy of Hormone Receptor-Positive/HER2-Negative Early Breast Cancer: What do we Know so Far?

The introduction of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors to the treatment of hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer is regarded as one of the greatest achievements of the last decades in breast oncology. To date, palbociclib, abemaciclib and ribociclib are the 3 approved CDK4/6 inhibitors that combined with endocrine therapy are now considered as the standard first-line treatment of metastatic HR+/HER2- breast cancer. The great success of these drugs in the setting of metastatic disease and the need to combat the high risk of recurrence have paved the way for a number of clinical trials to explore the use of CDK4/6 inhibitors in the neoadjuvant treatment of early breast cancer. In this review, we summarize the main findings of clinical trials that examined the use of CDK4/6 inhibitors in combination with hormone therapy or chemotherapy as neoadjuvant treatment of hormone receptor-positive and HER2-negative breast cancer. Active clinical trials that investigate different treatment schemes are also briefly presented and current limitations and future goals are discussed.

Real-world treatment patterns for palbociclib plus an aromatase inhibitor, or an aromatase inhibitor alone, for patients with metastatic breast cancer in the Flatiron Database

There are limited real-world comparative effectiveness data for palbociclib plus an aromatase inhibitor (AI) as a first-line (1L) treatment examining endpoints that require long term follow-up and post 1L progression. The Flatiron Health Analytic Database was used to characterize treatment and dosing patterns in patients with hormone receptor-positive/human epidermal growth factor 2-negative (HR+/HER2-) metastatic breast cancer (mBC) receiving palbociclib plus an AI vs an AI alone in routine US clinical practice. In addition, time to chemotherapy (TTC) and real-world progression-free survival (rwPFS) when combining 1L and second-line of therapy (rwPFS2) were assessed. Of 1324 patients who received palbociclib plus an AI between February 3, 2015 and March 31, 2020, 1110 (83.8%) started palbociclib at the recommended 125 mg/day dose. After stabilized inverse probability treatment-weighting (sIPTW), median TTC in patients treated with palbociclib plus an AI and AI alone was 37.4 months (95% confidence interval [CI], 33.7-40.7) and 29.2 months (95% CI, 26.8-33.5), respectively (hazard ratio [HR] = 0.77 [95% CI, 0.69-0.86], P < .0001); median rwPFS2 was 32.6 months (95% CI, 29.4-35.2) and 20.7 months (95% CI, 18.9-22.6), respectively (HR = 0.62 [95% CI, 0.54-0.70], P < .0001). Sensitivity analyses with propensity score matching showed similar results to sIPTW analyses. Results from this large real-world study examining additional effectiveness outcomes beyond 1L rwPFS and overall survival support the use of palbociclib plus an AI as a 1L treatment for patients with HR+/HER2- mBC.

Updated Review Article: Cyclin-Dependent Kinase 4/6 Inhibitor Impact, FDA Approval, and Resistance Pathways

Objective: To describe the mechanism of cyclin-dependent kinase (CDK) 4/6 inhibitors, mechanisms of resistance, and summarize various clinical trials used to determine the efficacy and safety of CDK4/6 inhibitor used for the treatment of hormone receptor-positive (HR+), human epidermal growth factor receptor 2 negative (HER2-), advanced or metastatic breast cancer. Data Sources: An extensive literature search using PubMed and notable sources was performed (2016 to February 2022) using the following search terms: CDK4/6 inhibitors, palbociclib, abemaciclib, ribociclib, CDK4/6 inhibitor resistance, FAT1 gene, luminal A breast cancer, luminal B breast cancer, HR+/HER2- breast cancer. Abstracts from conferences, national clinical trials, and drug monographs were reviewed. Study Selection and Data Extraction: Relevant clinical studies or those conducted in humans and updated clinical trials were considered. Data synthesis: The various clinical trials reviewed and results have led to numerous studies and expansions of U.S. Food and Drug Administration (FDA) approval. Although the use of CDK4/6 inhibitors has improved progression-free survival in patients with HR+, HER2- breast cancer, studies have shown that resistance pathways can cause cells to be insensitive to CDK4/6 inhibitors, leading to continued cell proliferation. Conclusions: CDK4/6 inhibitors are recommended as first-line therapy in combination with endocrine therapy for patients with HR+/HER2- advanced breast cancer. However, mutations and acquired resistance can occur that affect a patient's response to treatment. Additional research needs to be conducted on strategies to overcome resistance and determine how ethnicity plays a role in resistance pathways.

Real-world treatment patterns and effectiveness of palbociclib plus an aromatase inhibitor in patients with metastatic breast cancer aged 75 years or older

Background

Elderly patients are generally underrepresented in oncology clinical trials; therefore, real-world data are needed to inform clinical management of elderly patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer (mBC). This subanalysis of the P-REALITY X study (NCT05361655) evaluated palbociclib treatment patterns and comparative effectiveness of palbociclib plus an aromatase inhibitor (AI) versus an AI alone among patients with HR+/HER2- mBC aged ≥ 75 years treated in routine clinical practice in the United States.

Methods

This retrospective observational cohort study used electronic health records from the Flatiron Health Analytic Database. Palbociclib treatment patterns, overall survival (OS), real-world progression-free survival (rwPFS), and time to chemotherapy (TTC) were evaluated. Three methods were used for comparative analyses: (1) an unadjusted analysis, (2) stabilized inverse probability treatment weighting (sIPTW; primary analysis), and (3) propensity score matching (PSM; sensitivity analysis).

Results

A total of 961 patients aged ≥ 75 years with HR+/HER2- mBC were identified who started palbociclib plus an AI (n = 313) or an AI alone (n = 648) as first-line (1L) therapy between February 2015 and March 2020 (data cut-off: September 30, 2020). Among patients in the palbociclib plus an AI group with a documented palbociclib starting dose (n = 306), approximately 75% started palbociclib at 125 mg/day, and approximately 40% experienced dose adjustment. After sIPTW, patients treated with palbociclib plus an AI versus an AI alone had significantly improved OS (median of 43.0 vs. 32.4 months; hazard ratio [HR], 0.66 [95% confidence interval (CI), 0.51-0.84]; P = 0.0007), rwPFS (median of 20.0 vs. 15.0 months; HR, 0.72 (0.59-0.89); P = 0.0021), and TTC (median of 40.2 vs. 27.4 months; HR, 0.69 [0.55-0.87]; P = 0.0014). These significant improvements in OS, rwPFS, and TTC remained consistent in the unadjusted analysis and after PSM.

Conclusion

This real-world comparative analysis demonstrated that 1L palbociclib plus an AI is associated with improved effectiveness compared with an AI alone among patients with HR+/HER2- mBC aged ≥ 75 years. These findings support palbociclib plus an AI as a standard-of-care 1L treatment for elderly patients with HR+/HER2- mBC.

Barriers to gBRCA Testing in High-Risk HER2-Negative Early Breast Cancer

Despite the OlympiA trial demonstrating that early-stage, high-risk, HER2- germline BRCA1 and BRCA2 mutation (gBRCAm) positive breast cancer patients can benefit from PARPi in the adjuvant setting, the gBRCA testing rate in early-stage HR+/HER2- patients remains suboptimal compared to that in early-stage TNBC patients. To better understand the perceived barriers associated with gBRCA testing in HR+/HER2- disease, a quantitative survey was conducted across stakeholders (n = 430) including medical oncologists, surgeons, nurses, physician assistants, payers, and patients. This study revealed that while payers claim to cover gBRCA testing, poor clinician documentation and overutilization are key challenges. Therefore, payers place utilization management controls on gBRCA testing due to their impression that clinicians overtest. These controls have led to healthcare professionals experiencing payer pushback in the form of reimbursement limitations and denials. The perceived challenges to gBRCA testing stem from the lack of consensus dictating which patients are high risk and should be tested. While payers define high risk based on the CPS + EG score from the OlympiA trial, HCPs adopt a broader definition including genomic risk scores, lymph node involvement, and tumor grade and size. A dialogue to harmonize risk classification and testing eligibility across stakeholders is critical to address this disconnect and increase gBRCA testing in appropriate patients.

XENERA-1: a randomised double-blind Phase II trial of xentuzumab in combination with everolimus and exemestane versus everolimus and exemestane in patients with hormone receptor-positive/HER2-negative metastatic breast cancer and non-visceral disease

BACKGROUND

Xentuzumab is a humanised monoclonal antibody that binds to IGF-1 and IGF-2, neutralising their proliferative activity and restoring inhibition of AKT by everolimus. This study evaluated the addition of xentuzumab to everolimus and exemestane in patients with advanced breast cancer with non-visceral disease.

METHODS

This double-blind, randomised, Phase II study was undertaken in female patients with hormone-receptor (HR)-positive/human epidermal growth factor 2 (HER2)-negative advanced breast cancer with non-visceral disease who had received prior endocrine therapy with or without CDK4/6 inhibitors. Patients received a weekly intravenous infusion of xentuzumab (1000 mg) or placebo in combination with everolimus (10 mg/day orally) and exemestane (25 mg/day orally). The primary endpoint was progression-free survival (PFS) per independent review.

RESULTS

A total of 103 patients were randomised and 101 were treated (n = 50 in the xentuzumab arm and n = 51 in the placebo arm). The trial was unblinded early due to high rates of discordance between independent and investigator assessment of PFS. Per independent assessment, median PFS was 12.7 (95% CI 6.8-29.3) months with xentuzumab and 11.0 (7.7-19.5) months with placebo (hazard ratio 1.19; 95% CI 0.55-2.59; p = 0.6534). Per investigator assessment, median PFS was 7.4 (6.8-9.7) months with xentuzumab and 9.2 (5.6-14.4) months with placebo (hazard ratio 1.23; 95% CI 0.69-2.20; p = 0.4800). Tolerability was similar between the arms, with diarrhoea (33.3-56.0%), fatigue (33.3-44.0%) and headache (21.6-40.0%) being the most common treatment-emergent adverse events. The incidence of grade ≥ 3 hyperglycaemia was similar between the xentuzumab (2.0%) and placebo (5.9%) arms.

CONCLUSIONS

While this study demonstrated that xentuzumab could be safely combined with everolimus and exemestane in patients with HR-positive/HER2-negative advanced breast cancer with non-visceral disease, there was no PFS benefit with the addition of xentuzumab. Trial registration ClinicalTrials.gov, NCT03659136. Prospectively registered, September 6, 2018.

Real-world data for the renal safety of abemaciclib combined with bisphosphonate in HR+/HER2- advanced breast cancer

OBJECTIVE

Our study evaluated the renal safety of abemaciclib plus endocrine therapy (ET) with bisphosphonate as a treatment option for hormone receptor positive, human epidermal growth factor receptor 2 (HER-2) negative (HR+/HER2-) advanced breast cancer (ABC), especially with bone metastasis.

METHODS

Data were collected from HR+/HER2- ABC patients who received abemaciclib with ET between March 2021 and May 2022 in a single medical center in China. We performed an analysis of the change in serum creatine (Cr) and creatine clearance (CrCl), time to first abnormal Cr value, and Common Terminology Criteria for Adverse Events grade of increased creatinine.

RESULTS

A total of 210 patients were included in the final analysis, with a median age of 56 years and a median weight of 65 kg. Any grade laboratory-assessing increased Cr occurred in 87.1% of patients, while CrCl rarely went down to 30 ml/min. Associations between start dose with grade of increased Cr and menopausal status with alert value, which is defined as creatinine clearance <30 ml/min, were indicated.

CONCLUSION

This study shows that abemaciclib combined with bisphosphonate would be safe for renal function in HR+/HER2- ABC patients with bone metastases.

Progression-free survival on endocrine therapy, before or after chemotherapy, in hormone receptor-positive HER2-negative metastatic breast cancer

PURPOSE

A major question when treating HR+/HER2- metastatic breast cancer (MBC) is whether early introduction of chemotherapy (CT) increases endocrine resistance. We aimed to describe progression-free survival (PFS) under first endocrine therapy (ET) depending on whether given before or after CT in a large nationwide cohort, in the pre-CDK era.

METHODS

The real-life retrospective ESME database includes all patients with MBC whose first-line treatment was initiated between 2008 and 2014 in one of the 18 French Comprehensive Cancer Centres. Our primary objective was to compare PFS from start of first ET in patients with HR+/HER2- MBC who received ET or CT first.

RESULTS

We identified 6293 patients who received at least one ET line during their first two therapeutic lines for MBC. As first-line therapy, 3832 (60.9%) received ET alone (ET1 1st group), whilst 2461 (39.1%) received CT, including 2024 patients (32.2%) with maintenance ET after CT (ET1 after CT group). Median PFS under first ET was 12.4 months (95% CI 11.9-13.1) in ET 1st group vs. 12.6 months in ET1 after CT group (95% CI 12.1-13.4), HR 0.96 (95% CI 0.90-1.01, P = 0.1277).

CONCLUSIONS

PFS under first ET appears identical whether prescribed before or after chemotherapy. These data suggest chemotherapy does not promote endocrine resistance.

Real-world clinical profile, treatment patterns and patient-reported outcomes in a subset of HR+/HER2- advanced breast cancer patients with poor prognostic factors: data from an international study

Background

Patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer (ABC) and disease-related poor prognostic factors are not well characterized. We aimed to describe patient demographics, disease characteristics, treatment patterns and patient-reported outcomes in a subset of HR+/HER2− ABC patients with these factors [at the time when cyclin-dependent kinase (CDK) 4 and 6 inhibitors were being introduced] and understand how these factors informed treatment decisions at the time of the survey.

Methods

Real-world data were derived from a large, multinational, point-in-time survey of oncologists and their consulting patients with HR+/HER2− ABC in the EU5 and USA over March-June 2017, at the start of the changing treatment landscape. Analysis focused on four poor prognostic factors: visceral metastases, liver metastases (subset of visceral metastases), progesterone receptor-negative status and high tumor grade.

Results

In total, 2259 patients with HR+/HER2− ABC had records eligible for this analysis. At least one poor prognostic factor was present in 63% of patients (most common visceral metastases; least common progesterone receptor-negative status), with varying degrees of overlap between factors. For physician-reported outcomes, pain increased, whereas performance status and activities of daily living declined with presence of poor prognostic factors, especially liver metastases. No clear trends were observed for patient-reported outcomes. Treatment with combined endocrine therapy plus CDK4 and 6 inhibitors was infrequent, as these agents were entering the market.

Conclusions

More than 60% of the HR+/HER2− ABC Adelphi Real World Disease Specific Programme™ sample had ≥1 disease-related poor prognostic factor, and patients appeared to be heterogeneous regarding occurrence and distribution of these factors. These patients typically have increased pain and reduced performance status, highlighting the importance of implementing effective therapy with CDK4 and 6 inhibitors. Future studies could inform how the treatment landscape has evolved over time with respect to patients with poor prognostic factors.

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Some 63% of HR+/HER2− ABC patients in this sample had ≥1 disease-related factors more likely to confer a poorer prognosis

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Patients with these factors typically had increased pain and reduced performance status

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Chemotherapy was prescribed more frequently in patients with poor prognostic factors

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Introduction of CDK4 and 6 inhibitors saw more patients with poor prognostic factors receive endocrine therapy-based regimens

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This study is a baseline to understand the impact of these new treatments on prognosis and aggressive disease

Comparative effectiveness of first-line palbociclib plus letrozole versus letrozole alone for HR+/HER2- metastatic breast cancer in US real-world clinical practice

BACKGROUND

Findings from randomized clinical trials may have limited generalizability to patients treated in routine clinical practice. This study examined the effectiveness of first-line palbociclib plus letrozole versus letrozole alone on survival outcomes in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor-negative (HER2-) metastatic breast cancer (MBC) treated in routine clinical practice in the USA.

PATIENTS AND METHODS

This was a retrospective observational analysis of electronic health records within the Flatiron Health Analytic Database. A total of 1430 patients with ≥ 3 months of follow-up received palbociclib plus letrozole or letrozole alone in the first-line setting between February 3, 2015, and February 28, 2019. Stabilized inverse probability treatment weighting (sIPTW) was used to balance baseline demographic and clinical characteristics. Real-world progression-free survival (rwPFS) and overall survival (OS) were analyzed.

RESULTS

After sIPTW adjustment, median follow-up was 24.2 months (interquartile range [IQR], 14.2-34.9) in the palbociclib group and 23.3 months (IQR, 12.7-34.3) in those taking letrozole alone. Palbociclib combination treatment was associated with significantly longer median rwPFS compared to letrozole alone (20.0 vs 11.9 months; hazard ratio [HR], 0.58; 95% CI, 0.49-0.69; P < 0.0001). Median OS was not reached in the palbociclib group and was 43.1 months with letrozole alone (HR, 0.66; 95% CI, 0.53-0.82; P = 0.0002). The 2-year OS rate was 78.3% in the palbociclib group and 68.0% with letrozole alone. A propensity score matching analysis showed similar results.

CONCLUSIONS

In this "real-world" population of patients with HR+/HER2- MBC, palbociclib in combination with endocrine therapy was associated with improved survival outcomes compared with patients treated with letrozole alone in the first-line setting.

TRIAL REGISTRATION

Clinicaltrials.gov; NCT04176354.

Long-Term Pooled Safety Analysis of Palbociclib in Combination with Endocrine Therapy for Hormone Receptor-Positive/Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer: Updated Analysis with up to 5 Years of Follow-Up

Background

Previous studies demonstrated the tolerability of palbociclib plus endocrine therapy (ET). This analysis evaluated safety based on more recent cutoff dates and a longer palbociclib treatment exposure.

Patients and Methods

Data were pooled from three randomized studies of patients with hormone receptor‐positive/human epidermal growth factor receptor 2‐negative (HR+/HER2−) advanced breast cancer (ABC), including postmenopausal women who had not received prior systemic treatment for advanced disease (PALOMA‐1/‐2) and pre‐ and postmenopausal women who had progressed on prior ET (PALOMA‐3).

Results

Updated cutoff dates were December 21, 2017 (PALOMA‐1), May 31, 2017 (PALOMA‐2), and April 13, 2018 (PALOMA‐3). Total person‐years of treatment exposure were 1,421.6 with palbociclib plus ET (n = 872) and 528.4 with ET (n = 471). Any‐grade neutropenia and infections were more frequent with palbociclib plus ET (82.1% and 59.2%, respectively) than with ET (5.1% and 39.5%). The hazard ratios were 1.6 (p = .0995) for grade 3/4 infections, 1.8 (p = .4358) for grade 3/4 viral infections, 1.4 (p = .0001) for infections, and 30.8 (p < .0001) for neutropenia. Febrile neutropenia was reported in 1.4% of patients receiving palbociclib plus ET. Cumulative incidence of all‐grade hematologic adverse events in both arms peaked during the first year of treatment and plateaued over the 5 subsequent years. Interstitial lung disease was reported in 13 patients receiving palbociclib plus ET and 3 receiving ET.

Conclusion

This 5‐year, long‐term analysis demonstrated that palbociclib plus ET has a consistent and stable safety profile and is a safe treatment for patients with HR+/HER2− ABC.

Implications for Practice

Several treatments for patients with breast cancer are associated with long‐term or latent adverse events. This long‐term, 5‐year analysis demonstrated that palbociclib plus endocrine therapy has a consistent and stable safety profile without cumulative or delayed toxicities. These results further support palbociclib plus endocrine therapy as a safe and manageable treatment in clinical practice for patients with hormone receptor‐positive/human epidermal growth factor receptor 2‐negative advanced breast cancer.

This updated analysis based on data pooled from the three PALOMA studies is the largest long‐term analysis, to date, of the safety of a CDK4/6 inhibitor in combination with endocrine therapy for the treatment of advanced breast cancer.

Cost-effectiveness analysis of ribociclib plus letrozole versus palbociclib plus letrozole in the United Kingdom

OBJECTIVE

To evaluate the cost-effectiveness of ribociclib plus letrozole versus palbociclib plus letrozole in post-menopausal women with hormone receptor positive (HR+) and human epidermal growth receptor 2 negative (HER2-) advanced breast cancer from a UK payer perspective.

METHODS

A cohort-based partitioned survival model was developed to evaluate the cost-effectiveness of ribociclib plus letrozole versus palbociclib plus letrozole in post-menopausal women with HR+/HER2- advanced breast cancer over a lifetime horizon. The analysis was carried out from a National Health Services and Personal Social Services perspective, and results are presented in incremental costs per quality adjusted life years. Clinical data from three randomized controlled trials (MONALEESA-2, PALOMA-1 and PALOMA-2 studies) were used, and supplemented with available real world evidence. Costs categories comprised of drug acquisition, medical management, and treatment of adverse events. Healthcare resource utilization data were identified from literature and unit costs sourced from secondary sources. Utility values were derived from MONALEESA-2 study and were supported with values identified from literature. Both deterministic and probabilistic analyses were carried out to assess uncertainty.

RESULTS

In the base case, treatment with ribociclib plus letrozole increased mean progression free survival (PFS) by 4.1 months and overall survival by 5.0 months compared to palbociclib plus letrozole. Further, treatment with ribociclib plus letrozole resulted in cost-savings of £8464 and incremental QALYs of 0.261, demonstrating that treatment with ribociclib plus letrozole is dominant to treatment with palbociclib plus letrozole. The probabilistic analysis also yielded mean cost-savings of £7914 and mean QALY gain of 0.273. At willingness-to-pay threshold of £30 000 per QALY, treatment with ribociclib plus letrozole had a 92% probability of being cost-effective compared to palbociclib and letrozole.

CONCLUSIONS

The results of the analysis demonstrate that ribociclib plus letrozole treatment is both cost-saving and a cost-effective option amongst the available cyclin dependent kinase 4/6 inhibitors for the treatment of post-menopausal women with advanced breast cancer. The biggest driver of the cost savings were the lower acquisition costs of ribociclib.

Progression-free survival with endocrine-based therapies following progression on non-steroidal aromatase inhibitor among postmenopausal women with hormone receptor positive, human epidermal growth factor receptor-2 negative metastatic breast cancer: a network meta-analysis

OBJECTIVE

To quantify the comparative efficacy of currently available endocrine-based therapies (ETs) for postmenopausal women with hormone receptor positive, human epidermal growth factor receptor-2 negative (HR+/HER2-) metastatic breast cancer (mBC) after non-steroidal aromatase inhibitor (NSAI) progression.

DESIGN

Network meta-analysis (NMA).

METHODS

Randomized clinical trials of ETs for HR+/HER2- mBC were identified via a systematic literature review using MEDLINE, Embase, Cochrane Library and key conference proceedings. All trials met the following inclusion criteria: (1) included women with HR+/HER2- mBC; (2) previous treatment with ETs or chemotherapy as first-line therapy; (3) treatment with ET as monotherapy or in combination with targeted therapy; (4) progression-free survival (PFS) was reported; and (5) published in 2007 (when HER2 testing became standardized) or later. Regimens were compared using pairwise hazard ratios (HRs) and 95% credible intervals (CrIs) of PFS obtained from a Bayesian NMA. Treatments with different approved dosages were pooled into the same arm; anastrozole and exemestane were pooled as aromatase inhibitors (AIs) due to clinical similarities.

RESULTS

A total of 4 trials and 6 regimens (palbociclib + fulvestrant, everolimus + fulvestrant, everolimus + AI, fulvestrant + AI, fulvestrant and AI) were eligible for inclusion. Palbociclib + fulvestrant and everolimus + AI had 50% and 55% reduced hazard of progression or death vs. AI (95% CrI upper bound ≤1), respectively. Palbociclib + fulvestrant, everolimus + AI and everolimus + fulvestrant had 54%, 58% and 40% reduced hazard vs. fulvestrant (95% CrI upper bound ≤1), while palbociclib + fulvestrant and everolimus + AI had 52% and 55% reduced hazard vs. fulvestrant + AI (95% CrI upper bound ≤1), respectively.

CONCLUSION

Postmenopausal women with HR+/HER2- mBC who had previously failed an NSAI and received palbociclib + fulvestrant, everolimus + AI or everolimus + fulvestrant had longer PFS compared to those who received fulvestrant or AI alone.

Monitoring of Hematologic, Cardiac, and Hepatic Function in Post-Menopausal Women with HR+/HER2- Metastatic Breast Cancer

INTRODUCTION

In the treatment of metastatic breast cancer (mBC), regular monitoring is key in helping physicians to make informed clinical decisions, managing treatment side effects, and maintaining patients' quality of life. Therefore, we investigated the monitoring frequency in post-menopausal women with HR+/HER2- mBC stratified by first-line regimen.

METHODS

Treatment monitoring was assessed using two complementary data sources: a medical chart review (chart review analysis) and a commercial claims database (claims analysis). Women with post-menopausal HR+/HER2- mBC who initiated first-line therapy for mBC were selected and classified under three cohorts, based on treatment received: cyclin-dependent kinase 4/6 (CDK4/6) inhibitor (i.e., palbociclib-the only CDK4/6 approved at the time of the study), endocrine therapy (ET), and chemotherapy. Frequency of monitoring [complete blood count (CBC), electrocardiogram (EKG), and liver function test (LFT)] and laboratory abnormalities detected during the first line of therapy were analyzed.

RESULTS

In the chart review analysis, 64 US oncologists abstracted medical information on 401 eligible patients, including 210 CDK4/6 users, 121 ET users, 51 chemotherapy users; 19 patients used other regimens. All patients had ≥ 1 CBC; between 8.3% (ET users) and 39.5% (CDK4/6 users) had ≥ 1 EKG; and over 98% of patients had ≥ 1 LFT across all three cohorts. Among monitored patients, 64.6% had a CBC abnormality, with anemia (39.9%), leukopenia (27.4%), and neutropenia (26.7%) being the most common. Abnormal EKG readings were detected in 8.4, 0.0%, and 7.7% of CDK4/6, ET, and chemotherapy users, respectively. LFT abnormalities were detected in 14.1-26.0% of CDK4/6 and chemotherapy users, respectively. Similar frequency of monitoring was observed in the claims analysis, with the exception of EKG monitoring, for which the proportion of patients tested was higher.

CONCLUSION

Post-menopausal women with HR+/HER2- mBC receiving first-line therapy with CDK4/6, ET, or chemotherapy were regularly monitored regardless of the first-line regimen received.

FUNDING

Novartis Pharmaceuticals Corporation.

Recent advances of cyclin-dependent kinases as potential therapeutic targets in HR+/HER2- metastatic breast cancer: a focus on ribociclib

In normal cell cycle progression, transition of G0/G1 phase to synthesis (S) phase for breast and other cells is regulated by association of cyclin D and cyclin-dependent kinases 4 and 6 (CDK4/6) that leads to phosphorylation of retinoblastoma (Rb) protein. Imbalance of this cyclin D-CDK4/6-inhibitors of CDK4/6-Rb phosphorylation pathway is associated with tumorigenesis of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) breast cancers. Despite effective first-line endocrine therapy, HR+/HER2- metastatic breast cancers remain still incurable. Currently, advances in understanding of cell cycle checkpoints are evolving as promising strategy to target in treatment of various types of cancers including breast cancer. Therapies that target this cell cycle machinery in HR+/HER2- breast cancers are getting approval by the US Food and Drug administration (FDA) including ribociclib (LEE011). Ribociclib got the first FDA approval in March 13, 2017, as an initial therapy for HR+/HER2- advanced or metastatic breast cancer in combination with an aromatase inhibitor. This review, therefore, addresses the role of selective CDK4/6 inhibitors in advanced or metastatic breast cancer with a specific focus on ribociclib. Some findings of clinical trials involving ribociclib found pivotal benefits of ribociclib in HR+/HER2- metastatic breast cancer in terms of prolonging progression-free survival and objective response rates. Daily dosage range of the drug for such benefits is 50-900 mg with common daily doses of 400 or 600 mg and 600 mg in early and advanced breast cancer therapies, respectively. Along with its therapeutic benefits, however, more incident but manageable dose-limiting grade 3 or 4 toxicities, primarily hematologic adverse events, are common in patients treated with ribociclib. Generally, there are several active clinical trials undergoing to investigate the clinical efficacy and toxicity profile of the drug in various cancerous conditions other than breast cancer and will likely benefit patients with other cancer types.

Systematic Literature Review of the Impact of Endocrine Monotherapy and in Combination with Targeted Therapy on Quality of Life of Postmenopausal Women with HR+/HER2- Advanced Breast Cancer

INTRODUCTION

A major treatment goal for advanced breast cancer (ABC) is to maintain or ideally improve patient quality of life (QoL). Given the changing disease landscape, this systematic literature review (SLR) aims to assess the impact of endocrine therapies (ET), including ET monotherapy (ET mono) and ET combined with targeted therapy (ET + TT), on QoL of women with HR+/HER2- ABC.

METHODS

A SLR was conducted to identify randomized controlled trials (RCTs) meeting the following criteria: (1) included ET mono or ET + TT, (2) reported QoL outcomes, (3) focused on women with HR+/HER2- ABC, and (4) published after 2007 (when standardized HER2 testing became available). The databases searched included MEDLINE, EMBASE, Cochrane Library, and key conference proceedings from 2013 to 2016. QoL outcomes for ET mono, ET + TT, and comparisons between the two were summarized from the identified trials.

RESULTS

A total of 11 studies (representing 6 RCTs) were identified. The study populations included first-line (5 studies) and ET-failure settings (6 studies). Across settings, global health status (GHS) maintained or deteriorated slightly on these treatments during the trial period. Time to deterioration (TTD) in QoL measured by GHS was analyzed in 6 studies and 4 RCTs. In the first-line setting, reported median TTD in GHS was similar between ET mono and ET + TT (7.2-13.8 months in ET mono; 11.1 months in ET + TT). In the ET-failure setting, ET + TT showed significantly longer TTD vs. ET mono in GHS (median 5.6-8.4 months in ET mono and 8.3-11.7 months in ET + TT) and some additional domains.

CONCLUSIONS

ET + TT users experienced similar QoL in the first-line and ET-failure setting relative to patients on ET mono. Moreover, ET + TT users experienced better QoL outcomes in some domains in the ET-failure setting relative to ET mono users.

FUNDING

Novartis.

Comparison of medical costs and healthcare resource utilization of post-menopausal women with HR+/HER2- metastatic breast cancer receiving everolimus-based therapy or chemotherapy: a retrospective claims database analysis

OBJECTIVE

To analyze medical costs and healthcare resource utilization (HRU) associated with everolimus-based therapy or chemotherapy among post-menopausal women with hormone-receptor-positive, human-epidermal-growth-factor-receptor-2-negative (HR+/HER2-) metastatic breast cancer (mBC).

METHODS

Patients with HR+/HER2- mBC who discontinued a non-steroidal aromatase inhibitor and began a new line of treatment with everolimus-based therapy or chemotherapy (index therapy/index date) between July 20, 2012 and April 30, 2014 were identified from two large claims databases. All-cause, BC-related, and adverse event (AE)-related medical costs (in 2014 USD) and all-cause HRU per patient per month (PPPM) were analyzed for both treatment groups across patients' first four lines of therapies for mBC. Adjusted differences in costs and HRU between the everolimus and chemotherapy treatment group were estimated pooling all lines and using multivariable generalized linear models, accounting for difference in patient characteristics.

RESULTS

A total of 3298 patients were included: 902 everolimus-treated patients and 2636 chemotherapy-treated patients. Compared to chemotherapy, everolimus was associated with significantly lower all-cause (adjusted mean difference = $3455, p < 0.01) and BC-related ($2510, p < 0.01) total medical costs, with inpatient ($1344, p < 0.01) and outpatient costs ($1048, p < 0.01) as the main drivers for cost differences. Everolimus was also associated with significantly lower AE-related medical costs ($1730, p < 0.01), as well as significantly lower HRU (emergency room incidence rate ratio [IRR] = 0.83; inpatient IRR = 0.74; inpatient days IRR = 0.65; outpatient IRR = 0.71; BC-related outpatient IRR = 0.57; all p < 0.01).

CONCLUSIONS

This retrospective claims database analysis of commercially-insured patients with HR+/HER2- mBC in the US showed that everolimus was associated with substantial all-cause, BC-related, and AE-related medical cost savings and less utilization of healthcare resources relative to chemotherapy.

Clinical outcomes among HR+/HER2- metastatic breast cancer patients with multiple metastatic sites: a chart review study in the US

Background

Hormone receptor-positive, human epidermal growth factor receptor-2-negative (HR+/HER2−) is the most common type of metastatic breast cancer (mBC). While mBC patients generally have poor prognosis with limited progression-free survival (PFS) and overall survival (OS), those with multiple metastatic sites may have even worse clinical outcomes due to multiple organ involvement. This study aimed to compare clinical outcomes including PFS, time on treatment (TOT), and OS between HR+/HER2− mBC patients with multiple metastases versus those with a single metastasis in a real-world clinical setting.

Methods

This was a retrospective chart review study of postmenopausal HR+/HER2− mBC women who had failed a non-steroidal aromatase inhibitor in the adjuvant or metastatic setting and initiated a new treatment for mBC between 07/01/2012 and 04/15/2013. Patients were classified to one of two study groups (multiple metastases or single metastasis) based on the number of non-lymph-node metastases at the initiation of the new treatment. PFS, TOT and OS were compared between the two groups using Kaplan–Meier analyses and multivariable Cox proportional hazard models adjusting for patient disease and treatment characteristics. Separate Cox models were conducted including models with an interaction term between line of therapy and study group to assess the impact of multiple metastases on clinical outcomes across different lines of therapy.

Results

A total of 699 patient charts were collected, including 291 patients with multiple metastases and 408 single metastasis patients. Worse performance status and a higher proportion of prior chemotherapy for mBC were observed among patients with multiple metastases. Overall, patients with multiple metastases had significantly shorter PFS [adjusted hazard ratio (HR) = 1.55, 95 % confidence interval (CI) 1.21–1.98], TOT (adjusted HR = 1.33, 95 % CI 1.05–1.67), and OS (adjusted HR = 1.77, 95 % CI 1.15–2.74) than single metastasis patients. Similar outcomes were observed in each line of therapy.

Conclusions

Among HR+/HER2− mBC patients, patients with multiple metastases had significantly shorter PFS, TOT, and OS than single metastasis patients, highlighting the substantial clinical burden and unmet need for more efficacious treatments for the former group of patients.