Patterns of treatment and outcome of palbociclib plus endocrine therapy in hormone receptor-positive/HER2 receptor-negative metastatic breast cancer: a real-world multicentre Italian study

Palbociclib in Older Patients with Advanced/Metastatic Breast Cancer: A Systematic Review

BACKGROUND

Palbociclib in combination with endocrine therapy is approved for treatment of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer. In addition to clinical trials, several real-world studies have evaluated the effectiveness of palbociclib. With increased life expectancy in the general population, breast cancer in older women is also expected to increase.

OBJECTIVE

The aim was to systematically review evidence from both clinical trials and real-world studies for palbociclib treatment outcomes in older patients with HR+/HER2- advanced/metastatic breast cancer (a/mBC). Older patients are often underrepresented in clinical trials, and real-world evidence (RWE) will enrich the analysis of palbociclib outcomes in this subgroup of patients.

DESIGN

A systematic literature search in PubMed, EMBASE, and Cochrane Library through May 4, 2023, yielded 2355 unique articles. A total of 52 articles (13 and 39 articles reporting results from seven randomized controlled trials [RCTs] and 37 RWE studies, respectively) were included based on study eligibility criteria.

RESULTS

All RCTs used age cutoffs of ≥ 65 years to define older population (n = 722; 437 received palbociclib); all RWE studies, except one with an age cutoff of > 60 years, had age cutoffs of ≥ 65 years or higher to define older population (n = 9840; 7408 received palbociclib). Overall, in studies that compared efficacy (progression-free survival [seven RCTs, 20 RWE studies], overall survival [four RCTs, 11 RWE studies], tumor response [three RWE studies], and clinical benefit rate [one RCT, two RWE studies]) and safety outcomes (three RCTs, three RWE studies) between older and younger patients, palbociclib showed similar benefits, regardless of age. Results from two RCTs and two RWE studies showed that global quality of life (QoL) was maintained in older patients receiving palbociclib. Overall, palbociclib dose modifications (two RWE studies), dose reductions (one RCT, seven RWE studies), and treatment discontinuation rates (three RCTs, three RWE studies) were higher in older patients compared with younger patients; however, these differences did not appear to adversely impact efficacy outcomes.

CONCLUSIONS

In this systematic review, data from RCTs showed that palbociclib was effective, well tolerated, and maintained QoL in older patients with HR+/HER2- a/mBC. Palbociclib treatment in older patients in real-world settings was associated with similar clinical benefit as in RCTs.

PROSPERO REGISTRATION

CRD42023444195.

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.

A real-world study of the first use of palbociclib for the treatment of advanced breast cancer within the UK National Health Service as part of the novel Ibrance® Patient Program

BACKGROUND

The Ibrance® Patient Program was established to provide access to palbociclib for UK National Health Service (NHS) patients with metastatic breast cancer (MBC), pending a funding decision.

METHODS

Non-interventional cohort study involving a retrospective medical record review of patients commenced on palbociclib between April and December 2017 at eight UK centres. Primary outcomes included clinicopathological characteristics, treatment patterns, clinical outcomes and selected adverse events.

RESULTS

Overall, 191 patients were identified, median age of 57.0 years (range 24.3-90.9); 30% were diagnosed with de novo MBC; 72% received first-line and 10% as ≥ second-line treatment. Median progression-free survival (95% CI) was 22.8 months (16.5-not reached [NR]) in first-line; NR in patients with de novo MBC; 7.8 months (6.8-NR) in ≥ second-line (median follow-up: 24 months). Median overall survival (OS) was NR in the overall cohort; OS rate (95% CI) at 24 months was 74.2% (67.1-81.9%) in first-line; 82.1% (72.6-92.8%) in patients with de novo MBC; 55.0% (37.0-81.8%) in ≥ second-line. Forty-seven per cent of patients developed grade 3-4 neutropenia; 3% febrile neutropenia.

CONCLUSION

This study supports the effectiveness of palbociclib and demonstrates the benefit to patients of early access schemes that bridge the gap between regulatory approval and NHS funding for new medicines.

CLINICAL TRIAL REGISTRATION

Clinical trial: ClinicalTrial.gov:NCT03921866.

Effectiveness of palbociclib with aromatase inhibitors for the treatment of advanced breast cancer in an exposure retrospective cohort study: implications for clinical practice

BACKGROUND

New drugs for locally advanced or metastatic breast cancer have led to clinical benefits, aside with increasing costs to healthcare systems. The current financing model for health technology assessment (HTA) privileges real-world data. As part of the ongoing HTA, this study aimed to evaluate the effectiveness of palbociclib with aromatase inhibitors (AI) and compare it with the efficacy reported in PALOMA-2.

METHODS

A population-based retrospective exposure cohort study was conducted including all patients initiating treatment in Portugal with palbociclib under early access use and registered in the National Oncology Registry. The primary outcome was progression free survival (PFS). Secondary outcomes considered included time to palbociclib failure (TPF), overall survival (OS), time to next treatment (TTNT), and proportion of patients discontinuing treatment due to  adverse events (AEs). The Kaplan-Meier method was used and median, 1- and 2-year survival rates were computed, with two-sided 95% confidence intervals (95%CI). STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) guidelines for reporting observational studies were used.

RESULTS

There were 131 patients included. Median follow-up was 28.3 months (IQR: 22.7-35.2) and median duration of treatment was 17.5 months (IQR: 7.8-29.1). Median PFS was 19.5 months (95%CI 14.2-24.2), corresponding to a 1-year PFS rate of 67.9% (95%CI 59.2-75.2) and a 2-year PFS rate of 42.0% (95%CI 33.5-50.3). Sensitivity analysis showed median PFS would increase slightly when excluding those not initiating treatment with the recommended dose, raising to 19.8 months (95%CI 14.4-28.9). By considering only patients meeting PALOMA-2 criteria, we could observe a major difference in treatment outcomes, with a mean PFS of 28.8 months (95%CI 19.4-36.0). TPF was 19.8 months (95%CI 14.2-24.9). Median OS was not reached. Median TTNT was 22.5 months (95%CI 18.0-29.8). A total of 14 patients discontinued palbociclib because of AEs (10.7%).

CONCLUSIONS

Data suggest palbociclib with AI to have an effectiveness of 28.8 months, when used in patients with overlapping characteristics to those used in PALOMA-2. However, when used outside of these eligibility criteria, namely in patients with less favorable prognosis (e.g., presence of visceral disease), the benefits are inferior, even though still favorable.

Place in Therapy of Cyclin-Dependent Kinase 4/6 Inhibitors in Breast Cancer: A Targeted Literature Review

Cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) are the preferred regimen for patients with hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced or metastatic breast cancer. However, the optimal treatment sequencing for CDK4/6i with other available therapeutic options is unclear. We conducted a targeted literature review to identify the current evidence on CDK4/6i treatment patterns in patients with breast cancer. The search was initially conducted in October 2021 and subsequently updated in October 2022. Biomedical databases and gray literature were searched, and bibliographies of included reviews were screened for relevant studies. The search identified ten reviews published since 2021 and 87 clinical trials or observational studies published since 2015. The included reviews discussed CDK4/6i usage with or without endocrine therapy (ET) in first-line and second-line treatment for patients with HR+/HER2- advanced or metastatic breast cancer, followed by ET, chemotherapy, or targeted therapy with ET. Clinical studies reported similar treatment sequences consisting of ET, chemotherapy, or targeted therapy with ET prior to CDK4/6i with ET, followed by ET monotherapy, chemotherapy, targeted therapy with ET, or continued CDK4/6i with ET. Current evidence suggests CDK4/6i are effective for HR+/HER2- advanced or metastatic breast cancer in earlier lines of therapy. Efficacy of CDK4/6i as measured by progression-free survival and overall survival was similar within a line of therapy regardless of the type of prior therapy. Survival on different post-CDK4/6i treatments was also similar within the same line of therapy. Additional research is needed to investigate the optimal place in therapy of CDK4/6i and the sequencing of treatments following progression on CDK4/6i.

Palbociclib plus endocrine therapy in hormone receptor-positive and HER2 negative metastatic breast cancer: a multicenter real-world study in the northwest of China

BACKGROUND

Real-world data of Palbociclib are insufficient in China. This study aimed to investigate the treatment pattern and real-world outcomes in hormone receptor positive and human epidermal growth factor 2 receptor negative (HR+/HER2-) metastatic breast cancer (MBC) patients treated with Palbociclib in the northwest of China.

METHODS

HR+/HER2- MBC patients who received Palbociclib in 8 centers from July 2017 to September 2019 were retrospectively included in this study. Real-world objective response rate (ORR), progression-free survival (PFS) and safety profiles were analyzed. The survival curves were plotted by the Kaplan-Meier method to analyze PFS, which was verified by the log-rank test.

RESULTS

In total, 211 women were eligible for the analysis. A total of 85 patients (40.3%), 78 (37.0%), and 48 (22.7%) received Palbociclib in the first-, second-, third- or later-line setting, respectively. 46 patients achieved partial response and 145 patients experienced stable disease, with an ORR of 21.8% and a disease control rate of 90.5%. Following a median follow-up period of 14.2 months, the median PFS was 12.2 months (95% confidence interval, 10.1-14.3 m), and the median overall survival was not reached. Early Palbociclib initiation, sensitivity or acquired resistance to endocrine therapy, estrogen receptor and progesterone receptor double positivity, less than 3 metastatic sites, without visceral metastasis, bone metastasis only, without prior chemotherapy or endocrine therapy were associated with a prolonged PFS in MBC (All P < 0.05). The most common grade 3 or 4 adverse events (AE) was neutropenia (36.5%), and the most common nonhematologic AE was fatigue (10.9%). No patient experienced AE leading to treatment discontinuation.

CONCLUSION

Palbociclib plus endocrine therapy exhibited favorable effectiveness and manageable toxicities in the real-world setting, supporting their use in Chinese patients with HR+/HER2 - MBC.

Real-world outcomes from use of CDK4/6 inhibitors in the management of advanced/metastatic breast cancer in Asia

Background

Oestrogen receptor positive, human epidermal growth factor receptor-2 (HER2) negative breast cancer (BC) is the most frequently diagnosed BC subtype. Combinations of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) with anti-oestrogen therapy have led to improved survival compared with anti-oestrogen therapy alone for advanced/metastatic BC. The evaluation of CDK4/6i in the real-world facilitates treatment planning, insights into the incidence of drug toxicities, dose modifications including dose delays (DDs) and dose reductions (DRs) and improves prognostic accuracy in subgroups, for example geriatric patients, who are under-represented in clinical trials.

Methods

This multi-centre study analysed retrospective and prospective data from 456 patients treated with CDK4/6i between January 2015 and December 2020. We examined patient characteristics, variation in prescribing practices, efficacy and toxicity outcomes.

Results

In all, 456 patients were included in this study. The median age was 59 (range: 24-92). In total, 85 (19%) were ⩾70 years old. In all, 122 (27%) and 119 (26%) of patients were treated in the first-line and second-line settings, respectively. In total, 25 (5%), 31 (7%) and 145 (32%) of patients had brain, peritoneum and liver metastasis, respectively, at the time of CDK4/6i initiation. On univariate analysis, heavily pre-treated patients and those with distant metastases, involving the liver, brain or peritoneum, had significantly shorter progression-free survival (PFS) and 24-month overall survival (OS). Elderly patients (⩾70) had a shorter PFS; OS results were not mature. Majority of patients (n = 362, 80%) initiated treatment with the United States FDA-approved starting dose of CDK4/6i. In all, 330 (72%) had at least one DD and 217 (48%) patients required at least one DR, but these dose modifications were not associated with poorer survival outcomes. Patients age ⩾70 were more likely to require dose modifications leading to a lower treatment dose. The most common reason for DD/DR was neutropenia (60%) and the incidence of febrile neutropenia was only 2%.

Conclusions

Our study indicates CDK4/6i is effective and safe. Age ⩾ 70, distant metastases to liver, peritoneal or brain were negative prognostic factors. Age ⩾ 70 was associated with significantly increased requirement for dose modification; however, this did not impact survival outcomes. These findings provide reassurance that survival outcomes are not adversely affected in elderly patients when DD/DR is indicated.

The Renaissance of CDK Inhibitors in Breast Cancer Therapy: An Update on Clinical Trials and Therapy Resistance

Simple Summary

Cyclin-dependent kinase inhibitors (palbociclib (Ibrance), ribociclib (Kisqali), and abemaciclib (Verzenio)), targeting aberrant cell-cycle activity have been evaluated extensively in clinical trials. Significant delays in progression free survival and overall survival are now documented with each agent in estrogen receptor positive and human epidermal growth factor receptor two negative advanced breast cancer including luminal B breast cancer. Therapy resistance, driven by chromosomal instability, results in genomic rearrangements, activation of cell-cycle components (cyclin E/cdk2 in Rb⁻ tumors, cyclin D1 in growth factor activated pathways), and the immune response. Molecular analysis of therapy resistant tumors may provide the rational basis for new therapies (brivanib, CYC065, WEE1 kinase and other inhibitors). Luminal B breast cancer is enriched for cyclin D1 overexpression and the chromosomal instability gene signature. The molecular mechanisms governing chromosomal instability in luminal B breast cancer remain poorly understood. Co-targeting of chromosomal instability may potentially reduce the prevalent escape mechanisms that reduce the effectiveness of cyclin-dependent kinase inhibitors.

Abstract

Cyclin-dependent kinases (CDKs) govern cell-cycle checkpoint transitions necessary for cancer cell proliferation. Recent developments have illustrated nuanced important differences between mono CDK inhibitor (CDKI) treatment and the combination therapies of breast cancers. The CDKIs that are currently FDA-approved for breast cancer therapy are oral agents that selectively inhibit CDK4 and CDK6, include palbociclib (Ibrance), ribociclib (Kisqali), and abemaciclib (Verzenio). CDKI therapy is effective in hormone receptor positive (HR⁺), and human epidermal growth factor receptor two negative (HER2⁻) advanced breast cancers (ABC) malignancies, but remains susceptible due to estrogen and progesterone receptor overexpression. Adding a CDK4/6I to endocrine therapy increases efficacy and delays disease progression. Given the side effects of CDKI, identifying potential new treatments to enhance CDKI effectiveness is essential. Recent long-term studies with Palbociclib, including the PALLAS and PENELOPE B, which failed to meet their primary endpoints of influencing progression-free survival, suggest a deeper mechanistic understanding of cyclin/CDK functions is required. The impact of CDKI on the anti-tumor immune response represents an area of great promise. CDKI therapy resistance that arises provides the opportunity for specific types of new therapies currently in clinical trials.

Real-world effectiveness of palbociclib plus fulvestrant in advanced breast cancer: Results from a population-based cohort study

Background

Real-world (RW) data may provide valuable information on the effectiveness and safety of medicines, which is particularly relevant for clinicians, patients and third-party payers. Evidence on the effectiveness of palbociclib plus fulvestrant is scarce, which highlights the need of additional studies. The aim of this study was to evaluate the effectiveness of palbociclib plus fulvestrant in advanced breast cancer (ABC).

Materials and methods

We conducted a population-based retrospective cohort study and cases of interest were identified through the Portuguese National Cancer Registry database and additional data sources. Patients aged≥18 years, diagnosed with ABC and exposed to palbociclib plus fulvestrant between May 31, 2017 and March 31, 2019 were included. Patients were followed-up until death or cut-off date (February 28, 2021). Primary outcome was rw-progression-free survival (rwPFS). Secondary outcomes were rw-overall survival (rwOS), rw-time to palbociclib failure (rwTPF) and rw-time to next treatment (rwTTNT).

Results

A total of 210 patients were included. Median age was 58 years (range 29–83) and 99.05% were female. Median follow-up time was 23.22 months and, at cut-off date, treatment had been discontinued in 189 patients, mainly due to disease progression (n = 152). Median rwPFS was 7.43 months (95% confidence interval [CI] 6.28–9.05) and 2-year rwPFS was 16.65% (95%CI 11.97–22.00). Median rwOS was 24.70 months (95%CI 21.58–29.27), median rwTPF was 7.5 months (95%CI 6.51–9.08) and median rwTTNT was 11.74 months (95%CI 10.33–14.08).

Conclusion

Palbociclib plus fulvestrant seems an effective treatment for ABC in real-world context. Compared to registrations studies, rwPFS and rwOS were shorter in real-life setting.

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Palbociclib plus fulvestrant seems to be an effective therapy for ABC in real-world.

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Median rwPFS and rwOS were estimated at 7.43 and 24.70 months, respectively.

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Our data suggest lower effectiveness in real-world than the efficacy reported.

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Treatment was discontinued due to AEs in 8.09% of patients, suggesting good tolerability.

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Registries may generate effectiveness data and support clinical and HTA decisions.

Palbociclib plus endocrine therapy significantly enhances overall survival of HR+/HER2- metastatic breast cancer patients compared to endocrine therapy alone in the second-line setting-a large institutional study

Cyclin-dependent-kinase-4/6 inhibitor (CDKi) plus endocrine therapy (ET) is standard of care for patients with advanced hormone receptor (HR)-positive, HER2-negative breast cancer (BC). The Breast Medical Oncology database at MD Anderson Cancer Center (MDACC) was analyzed to assess effectiveness of the CDKi palbociclib plus ET compared to ET alone. From a total of 5402 advanced HR+ HER2- BC patients referred to MDACC between 1997 and 2020, we identified eligible patients who received palbociclib in combination with first- (n=778) and second-line (n=410) ET. We further identified "control" patients who received ET alone in the first- (n=2452) and second-line (n=1183) settings. Propensity score matching analysis was conducted to balance baseline demographic and clinical characteristics between palbociclib and control cohorts to assess the effect of palbociclib treatment on progression-free survival (PFS) and overall survival (OS). For propensity-matched-cohort in the first-line setting (n=708), palbociclib group had significantly longer median PFS (17.4 vs. 11.1 months; p<0.0001) compared to controls. Median OS (44.3 vs. 40.2 months) did not show a statistically significant benefit in the first line setting. However, in the second-line setting, with 380 propensity-matched-cohort, the palbociclib group had significantly longer PFS (10 vs 5 months, p<0.0001) as well as OS (33 vs 24 months; p < 0.022), compared to controls. We conclude that in this single center analysis of a large cohort of metastatic HR+ HER2- BC patients, palbociclib in combination with ET was associated with improved PFS in both first- and second-line settings and OS in the second-line setting compared with ET alone cohort.

First-Line Treatment with a Cyclin-Dependent Kinase 4/6 Inhibitor Plus an Aromatase Inhibitor for Metastatic Breast Cancer in Alberta

In this analysis, we describe population-based outcomes for first-line treatment with a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) combined with an aromatase inhibitor (AI). All patients who were prescribed CDK4/6i + AI from January 2016 through June 2019 were included. Patient demographics, tumour and treatment characteristics were collected and described. Survival distributions were estimated using the Kaplan–Meier method. Multivariate analysis (MVA) was constructed to examine associations between potentially prognostic clinical variables and progression-free survival (PFS). In total, 316 patients were included. The median age was 61 years. After a median follow-up of 28.1 months, the median PFS was 37.9 months (95% CI, 26.7–NR). In the MVA, PR-negative tumour (HR, 2.37; 95% CI, 1.45–3.88; p = 0.001) and CDK4/6i dose reduction (HR, 1.51; 95% CI, 1.06–2.16; p = 0.022) predicted worse PFS. Median overall survival (OS) was not reached. The 30-month and 36-month OS rates were 74% and 68%, respectively. Of patients who progressed, 89% received second-line treatment. Median time to progression on second-line chemotherapy was 9.0 (5.8–17.6) months, and median time to progression on second-line hormonal therapy +/− targeted agent was 4.0 (3.4–8.6) months (p = 0.012). CDK4/6i + AI as first-line treatment for HR-positive, HER2-negative MBC in Alberta is justified based on favourable PFS and early OS outcomes.