Palbociclib as a first-line treatment in oestrogen receptor-positive, HER2-negative, advanced breast cancer not cost-effective with current pricing: a health economic analysis of the Swiss Group for Clinical Cancer Research (SAKK)

Cost-Effectiveness Analysis of Abemaciclib plus Fulvestrant versus Placebo plus Fulvestrant in Patients with Hormone Receptor-Positive, ERBB2-Negative Breast Cancer

PURPOSE

Abemaciclib is a selective and potent small-molecule inhibitor of cyclin-dependent kinase 4 and 6 (CDK4 and CDK6) which is administered orally. Compared to placebo plus fulvestrant (PF), abemaciclib plus fulvestrant (AF) significantly improved progression-free survival (PFS) and overall survival (OS). However, an economic evaluation of these two treatments is currently lacking. The purpose of this article was to evaluate the cost-effectiveness of the two treatments for HR*, HER2- advanced breast cancer (ABC) in the USA.

METHODS

A Markov simulation model was constructed using data from a published clinical trial (MONARCH 2). The two simulated treatment strategies included AF or PF. Costs were obtained from the clinical trials and the website, and utility was derived from the published literature. Incremental cost-effectiveness ratios (ICERs) were calculated to compare the two treatment strategies.

RESULTS

The total costs were USD 400,377.43 and USD 89,937.77 for AF and PF treatment, respectively. The AF treatment produced 2.09 long-term quality-adjusted life years (QALYs), and the PF treatment produced 1.08 QALYs. Hence, patients who received AF treatment spent an additional USD 310,439.66 and generated an increase of 1.01 QALYs, resulting in an ICER of USD 307,366 per QALY. At current prices, AF was not cost-effective assuming a willingness-to-pay threshold of USD 150,000 per QALY gained.

CONCLUSION

Despite significant gains in PFS over AF, it is not a cost-effective treatment for HR*, HER2- ABC in the USA at current drug prices.

Pharmacoeconomic evaluations of CDK4/6 inhibitors plus endocrine therapy for advanced hormone receptor-positive (HR+) and human epidermal growth factor receptor-2 negative (HER2-) breast cancer: a systematic review

Background

Hormone receptor-positive (HR+) and human epidermal growth factor receptor-2 negative (HER2−) breast cancer is the most common molecular subtype of breast cancer in many countries, and endocrine therapy remains a mainstay in its treatment. Cyclin-dependent kinase (CDK) 4/6 inhibitors are a new class of targeted agents administered orally that are recommended being used in combination with endocrine therapy as first and second line treatments for advanced HR+/HER2− breast cancer. However, their high prices largely hinder using these drugs in real world settings. To offer a new basis for future research, we investigated the cost-effectiveness of combinations of CDK4/6 inhibitors with endocrine therapy in the treatment of advanced HR+/HER2− breast cancer.

Methods

We systematically searched several frequently used databases and identified economic evaluations published from February 2015 to April 2021. The systematic review was performed after retrieving the literatures and extracting data based on inclusion and exclusion criteria. The quality of each selected economic evaluation was assessed by the Consolidated Health Economic Evaluation Reporting Standards (CHEERS).

Results

The literature search yielded 161 articles, among which fourteen studies (15 articles) with CHEER scores ranging from 58.33% to 87.50% entered the final analysis. Markov models were used in most studies. Based on the currently available data, CDK4/6 inhibitors plus endocrine therapy were less cost-effective in first- or second-line treatment of patients with HR+/HER2− advanced breast cancer. However, ribociclib plus letrozole was more cost-effective than palbociclib plus letrozole in the first-line treatment of postmenopausal women. The economic impacts of CDK4/6 inhibitors plus endocrine therapy in non-postmenopausal patients or second-line therapy cannot be fully evaluated due to the limited number of studies. The three most common factors affecting economic outcomes were the prices of CDK4/6 inhibitors, hazard ratios for progression-free survival and overall survival, and health status utility values.

Discussion

CDK4/6 inhibitors plus endocrine therapy have shown significantly improved efficacy outcomes in HR+/HER2− metastatic breast cancer (mBC)/advancer breast cancer (ABC) first-line and second-line treatment for endocrine-sensitive and endocrine-resistant populations, while more potential fields including neoadjuvant and adjuvant settings are being identified to benefit a wider range of breast cancer patients. Meanwhile, risk of severe adverse events that more likely to happen in patients treated with CDK4/6 inhibitors can lead to reduced life quality and higher medical costs patients need to afford. The adverse drug reaction related cost in several economic burden studies were explored to be primarily driven by hospitalizations and outpatient, and assessment of cost associated with CDK4/6 inhibitors adverse events is worth further developing. Drug wastage costs were found higher in palbociclib regimen than ribociclib regimen due to different dosing patterns. Moreover, current economic evaluations showed that ribociclib plus letrozole had better economic benefits than palbociclib plus letrozole for first-line treatment of postmenopausal women with HR+/HER2− ABC.

Handling Uncertainty in Cost-Effectiveness Analysis: Budget Impact and Risk Aversion

Methods to handle uncertainty in economic evaluation have gained much attention in the literature, and the cost-effectiveness acceptability curve (CEAC) is the most widely used method to summarise and present uncertainty associated with program costs and effects in cost-effectiveness analysis. Some researchers have emphasised the limitations of the CEAC for informing decision and policy makers, as the CEAC is insensitive to radial shifts of the joint distribution of incremental costs and effects in the North-East and South-West quadrants of the cost-effective plane (CEP). Furthermore, it has been pointed out that the CEAC does not incorporate risk-aversion in valuing uncertain costs and effects. In the present article, we show that the cost-effectiveness affordability curve (CEAFC) captures both dimensions of the joint distribution of incremental costs and effects on the CEP and is, therefore, sensitive to radial shifts of the joint distribution on the CEP. Furthermore, the CEAFC also informs about the budget impact of a new intervention, as it can be used to estimate the joint probability that an intervention is both affordable and cost-effective. Moreover, we show that the cost-effectiveness risk-aversion curve (CERAC) allows the analyst to incorporate different levels of risk-aversion into the analysis and can, therefore, be used to inform decision-makers who are risk-averse. We use data from a published cost-effectiveness model of palbociclib in addition to letrozole versus letrozole alone for the treatment of oestrogen-receptor positive, HER-2 negative, advanced breast cancer to demonstrate the differences between CEAC, CEAFC and CERAC, and show how these can jointly be used to inform decision and policy makers.

Palbociclib in breast cancer neoadjuvant setting

Cyclin-dependent kinase 4/6 inhibitors represent a major advance in breast cancer treatment, emerging as the standard of care of the initial treatment of hormone receptor-positive and HER2-negative metastatic breast cancer. Their activity in this subset of patients leads to interest in their use in the adjuvant and neoadjuvant settings. This case report presents a real-life case of cyclin-dependent kinase 4/6 inhibitors use in a patient initially considered to have stage IV luminal HER2-negative breast cancer with liver metastasis. The discrepancy of treatment response between the breast tumor and liver node led to a repetition of the liver biopsy, which revealed metastasis of a neuroendocrine tumor of unknown primary. The breast tumor showed a partial response, and the initial therapeutic strategy was then redefined for curative intent. While cyclin-dependent kinase 4/6 inhibitors are not yet approved for clinical practice in the neo / adjuvant treatment of hormone receptor-positive breast cancer, this case report portrays a successful example of its application in a neoadjuvant setting.

Elective Discontinuation of CDK4/6 Inhibitors in Patients with Metastatic Hormone Receptor-Positive, Her-2-Negative Breast Cancer: A Retrospective Single-Center Experience

INTRODUCTION

Cyclin-dependent 4/6 kinase (CDK4/6) inhibitors given with endocrine therapy until disease progression are standard of care in the treatment of women with advanced HR-positive Her-2-negative breast cancer. No data are available if therapy can be safely de-escalated to endocrine monotherapy in patients with long-lasting disease control.

METHODS

We performed a retrospective analysis on the clinical course of 22 patients at our center who received CDK4/6 inhibitors with aromatase inhibitors or fulvestrant. All patients had at least stable disease for >6 months and made a joint decision with their provider to electively discontinue CDK4/6 inhibitors. Best objective response (BOR) at treatment discontinuation, progression-free survival, and re-treatment characteristics were recorded.

RESULTS

Of 138 patients who received CDK4/6 inhibitors as first- or second-line therapy at our center, 22 met the inclusion criteria. Median duration of CDK4/6 treatment was 18 months (range 6-45). BOR was complete response in 1, partial response in 8, and stable disease in 13 patients. After a median duration of endocrine monotherapy of 9.5 months (range 5-44 months), 6 of 22 patients had progressive disease (1 local relapse and 5 systemic progression). All patients with disease progression had at least stable disease to chemotherapy (N = 1) or re-treatment with CDK4/6 inhibitors (N = 4).

CONCLUSION

Elective discontinuation of CDK4/6 inhibitors is feasible in patients with long-lasting disease stabilization. This strategy should be evaluated in prospective trials.

Cost-effectiveness of ribociclib as initial treatment for premenopausal women with advanced breast cancer in Singapore

BACKGROUND

CDK4/6 inhibitors have shown promising results for treating advanced breast cancer (ABC) and are routinely used in Singapore. In view of their high costs, it is important to assess their relative value compared to existing standards of care in the local setting.

AIMS

This study evaluates the cost-effectiveness of adding ribociclib to goserelin and a nonsteroidal aromatase inhibitor or tamoxifen as initial therapy for premenopausal women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) ABC in Singapore.

METHODS

A partitioned survival model with four health states (progression-free on first-line treatment, progression-free on second-line treatment, progressed disease, and death) was developed from a healthcare system perspective over a 10-year time horizon. Key clinical inputs were derived from the MONALEESA-7 trial, and survival curves were extrapolated beyond the trial period. Health state utilities were derived from the literature and direct medical costs were obtained from local public healthcare institutions. A discount rate of 3% was applied to both costs and outcomes. One-way deterministic and probabilistic sensitivity analyses were conducted to explore uncertainties.

RESULTS

The base-case analysis resulted in an incremental cost-effectiveness ratio (ICER) of SGD197, 667 per quality-adjusted life-year. Sensitivity analyses showed that the ICER was sensitive to the survival parametric distribution, ribociclib price, time horizon, and utility weights used. Even when these were varied, ICERs remained high and not cost-effective in the local context.

CONCLUSION

At its current price, adding ribociclib to endocrine therapy is unlikely to be cost-effective in Singapore for HR+, HER2- ABC. Results from this study are useful to inform future funding decisions for CDK4/6 inhibitors alongside other factors including clinical effectiveness, safety, and budget impact considerations.

Real-World Clinical and Economic Outcomes Associated with Palbociclib for HR-Positive/HER2 Negative Metastatic Breast Cancer: A Commentary

Despite the achieved advancement in pharmacological cancer treatments, the majority of postmenopausal women with hormone receptor-positive metastatic breast cancer (mBC) will experience disease progression. Research into alternative therapies with improved efficacy and reduced side effects has led to the development of a new class of oral anticancer medications, the cyclin-dependent kinase (CDK) 4/6 inhibitors, which include palbociclib, ribociclib, and abemaciclib. Nonetheless, there is growing evidence that the effectiveness of oral anticancer medications is sub-optimal, being influenced by low adherence, sociodemographic factors, and adverse effect profiles. In addition, there is a disconnect between the high price tags of CDK 4/6 inhibitors and their observed effectiveness, raising questions about their value. Currently, the existing knowledge base on the effectiveness and cost-effectiveness of newer oral anticancer medications in understudied populations with possible health disparities is scant. This commentary discusses what is known about palbociclib's clinical effectiveness, safety, and adherence and suggests the need for further studies of real-world effectiveness and cost-effectiveness to help establish the value of newer oncologic drugs, such as palbociclib. DISCLOSURES: No funding supported the writing of this article. The authors have nothing to disclose.

Cyclin-dependent kinase 4/6 inhibitors for the management of advanced or metastatic breast cancer in women

PURPOSE

The pharmacology, clinical activity, safety, and place in therapy of the cyclin-dependent kinase (CDK) inhibitors palbociclib, ribociclib, and abemaciclib are reviewed.

SUMMARY

CDK 4 and CDK 6 are downstream agents in the estrogen signaling pathway that control entry into the cell cycle. CDK4/6 inhibition may prevent tumor cell progression in the cell cycle. Three CDK4/6 inhibitors (palbociclib, ribociclib, and abemaciclib) are available for women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer. These medications' indications in the treatment of HR+/HER2- advanced breast cancer include use with an aromatase inhibitor (AI) as initial therapy in postmenopausal women and with fulvestrant in women whose disease progressed during endocrine therapy. Ribociclib is also indicated as initial therapy with an AI in premenopausal or perimenopausal women and as initial therapy with fulvestrant in postmenopausal women. Abemaciclib is also indicated as monotherapy in women with disease progression after endocrine therapy and prior chemotherapy. A significant increase in progression-free survival (PFS) was seen with use of all 3 agents as initial therapy with an AI in controlled trials. Each agent also was demonstrated to produce a significant increase in PFS when used with fulvestrant in women whose disease progressed with prior endocrine therapy. Neutropenia is a dose-limiting adverse effect of palbociclib and ribociclib. Fatigue is more common with use of palbociclib and abemaciclib, and gastrointestinal effects are more common with abemaciclib use.

CONCLUSION

CDK4/6 inhibitors have significant demonstrated clinical activity in combination with AIs or fulvestrant in women with HR+/HER2- advanced or metastatic breast cancer and are becoming a standard of care in these patients.

Cost-Effectiveness Analysis of Adding Palbociclib as a Second-Line Endocrine Therapy for HR+/HER2- Metastatic Breast Cancer From the US and Chinese Perspectives

PURPOSE

As a second-line endocrine therapy for hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR⁺/HER2^-) metastatic breast cancer, palbociclib has demonstrated significant efficacy in prolonging progression-free survival when added to a regimen containing fulvestrant. The objective of this study was to evaluate the cost-effectiveness of palbociclib from the perspectives of the United States and China.

METHODS

We developed a Markov model to estimate lifetime costs, overall life-years gained, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs). One-way and probabilistic sensitivity analyses were performed to predict the uncertainty of the model developed. The time horizon was 10 years, and the perspective was that of the payer.

FINDINGS

Within a 10-year time horizon, the palbociclib-containing strategy provided an additional 0.568 QALY, with an ICER of 88,854 USD/QALY, in the United States. When palbociclib cost 30%, 20%, and 10% of the current price, the ICERs were 185,526, 42,193, and 98,860 USD/QALY, respectively. In China, the ICER was 182,779 USD/QALY. When palbociclib cost 30%, 20%, and 10% of the current price, the ICERs were 79,558, 64,812, and 50,066 USD/QALY, respectively. In order to meet 50% probability of cost-effectiveness, the estimated price would have to be 32.52 USD/100 mg at a willingness-to-pay threshold of 58,480 USD/QALY (3 × per-capita domestic product of Beijing, China).

IMPLICATIONS

Adding palbociclib to a regimen of fulvestrant is unlikely to be cost-effective as a second-line endocrine therapy for HR⁺/HER2^- metastatic breast cancer (MBC) with at the current price in the United States and China. For widely meeting the treatment demands of patients, it may be a better option to decrease the price or provide more patients with a financial assistance program for palbociclib both in the United States and in China.

An updated systematic review of the cost-effectiveness of therapies for metastatic breast cancer

PURPOSE

The goal of this systematic review is to provide an update to the review by Pouwels et al. by conducting a systematic review and an assessment of the reporting quality of the economic analyses conducted since 2014.

METHODS

This systematic review identified published articles focused on metastatic breast cancer treatment using the Medline/PubMed and Scopus databases and the following search criteria: (((cost effectiveness[MeSH Terms]) OR (cost effectiveness) OR (cost-effectiveness) OR (cost utility) OR (cost-utility) OR (economic evaluation)) AND (("metastatic breast cancer") OR ("advanced breast cancer"))). The reporting quality of the included articles was evaluated using the International Society of Pharmacoeconomics and Outcomes Research (ISPOR) Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist.

RESULTS

Of the 256 identified articles, 67 of the articles were published after October 2014 when the prior systematic review stopped its assessment (Pouwels et al. in Breast Cancer Res Treat 165:485-498, 2017). From the 67 articles, we narrowed down to include 17 original health economic analyses specific to metastatic or advanced breast cancer. These articles were diverse with respect to methods employed and interventions included.

CONCLUSION

Although each of the articles contributed their own analytic strengths and limitations, the overall quality of the studies was moderate. The review demonstrated that the vast majority of the reported incremental cost-effectiveness ratios exceeded the typically employed willingness to pay thresholds used in each country of analysis. Only three of the reviewed articles studied chemotherapies rather than treatments targeting either HER2 or hormone receptors, demonstrating a gap in the literature.

Budget impact of including ribociclib in combination with letrozole on US payer formulary: first-line treatment of post-menopausal women with HR+/HER2- advanced or metastatic breast cancer

OBJECTIVES

The combination of a cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitor with the aromatase inhibitor letrozole is a safe and effective alternative to letrozole monotherapy for first-line hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer. This study evaluates the budget impact of using the CDK 4/6 inhibitor ribociclib plus letrozole as a first-line treatment option for postmenopausal women with HR+/HER2- advanced breast cancer, from a United States (US) payer perspective.

METHODS

A cohort-based budget impact model was used to calculate the incremental cost of introducing ribociclib plus letrozole over three years for the target population. The analysis compared two scenarios: treatment options excluding or including ribociclib plus letrozole. Market shares were derived from market research and the assumption was the introduction of ribociclib plus letrozole would only displace existing CDK-based therapies. Treatment duration was based on the median time to treatment discontinuation or median progression-free survival for first-line treatment, and on clinical trial data for second- and third-line treatment. Acquisition costs were based on wholesale acquisition costs and considered co-payment. Costs for drug administration and monitoring, subsequent therapy, and relevant adverse events were included.

RESULTS

Of 1 million insured members, 263 were eligible for CDK 4/6 inhibitor treatment. Cumulative total savings with ribociclib plus letrozole were $3.01M over three years, corresponding to a cumulative incremental cost saving of $318.11 per member treated per month.

CONCLUSIONS

In the US, ribociclib plus letrozole represents a cost-saving first-line treatment option for postmenopausal women with HR+/HER2- advanced breast cancer.

Cost-effectiveness analysis of ribociclib versus palbociclib in the first-line treatment of HR+/HER2- advanced or metastatic breast cancer in Spain

PURPOSE

The aim of this study was to evaluate the cost-effectiveness of ribociclib compared to palbociclib, both in combination with letrozole, in the first-line treatment of postmenopausal women with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer (ABC) from the perspective of the Spanish National Health System (NHS).

PATIENTS AND METHODS

Disease progression was simulated with a partitioned survival model developed from the parameterization and extrapolation of survival curves of postmenopausal women with HR+/HER2- ABC from clinical trials with ribociclib or palbociclib, both in combination with letrozole. The model was structured on the basis of three health states (progression-free, progressed disease, and death), with a 1-month cycle length and inclusion of subsequent treatments administered for disease progression, over a time horizon of 15 years. Clinical, economic, and quality of life parameters were drawn from clinical trials and the literature. The use of resources and clinical practice in the Spanish setting was validated by a panel of experts. The Spanish NHS perspective was adopted, taking into account exclusively direct health costs from 2017 expressed in Euros. Drug prices used were the reported ex-factory prices. Uncertainty of the parameters and robustness of the results were evaluated using deterministic and probabilistic sensitivity analyses (2,000 iterations).

RESULTS

This cost-effectiveness analysis showed a greater benefit (0.437 and 0.285 life-years gained [LYGs] and quality-adjusted life years [QALYs] gained, respectively) and a slightly higher cost (€439.86) for ribociclib+letrozole compared to palbociclib+letrozole. The resulting incremental cost-effectiveness and cost-utility ratios were €1,007.69 per LYG and €1,543.62 per QALY gained, respectively. The results of the multiple sensitivity analyses showed limited dispersion of the outcomes, thus corroborating their robustness.

CONCLUSION

From the NHS perspective, considering the most commonly established willingness-to-pay thresholds in the Spanish setting, ribociclib+letrozole would represent a cost-effective therapeutic option compared to palbociclib+letrozole in the first-line treatment of HR+/HER2- ABC in postmenopausal women.

Cost-Effectiveness of Ribociclib plus Letrozole Versus Palbociclib plus Letrozole and Letrozole Monotherapy in the First-Line Treatment of Postmenopausal Women with HR+/HER2- Advanced or Metastatic Breast Cancer: A U.S. Payer Perspective

BACKGROUND

U.S. regulatory approvals of the cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitors ribociclib and palbociclib as add-ons to letrozole greatly enhance the prospects for treating postmenopausal women with hormone receptor-positive (HR+)/human epidermal receptor 2-negative (HER2-) advanced or metastatic breast cancer. Clinical trials have established that the combination of a CDK 4/6 inhibitor with letrozole can significantly improve progression-free survival (PFS) versus letrozole monotherapy and is safe and well tolerated. Cost-effectiveness studies are required to inform payers and clinical decision makers on the money value of combination treatment in clinical practice.

OBJECTIVE

To evaluate the cost-effectiveness of ribociclib plus letrozole versus palbociclib plus letrozole and versus letrozole monotherapy in the first-line treatment of postmenopausal women with HR+/HER2- advanced or metastatic breast cancer from a U.S. private third-party payer perspective.

METHODS

A partitioned survival model including 3 health states (progression free, with either overall response or stable disease; progressed disease; and death) simulated lifetime costs and outcomes over a 40-year lifetime horizon with a 1-month cycle length. Clinical efficacy data (PFS and overall survival [OS]) were derived from a phase III trial of ribociclib plus letrozole (MONALEESA-2; NCT01958021), a phase II trial of palbociclib plus letrozole (PALOMA-1; NCT00721409), and a Bayesian network meta-analysis. Health care costs included drug acquisition and monitoring, disease management, subsequent therapies, and serious drug-related adverse events. Effectiveness was measured in life-years, derived from survival projections, and in quality-adjusted life-years (QALYs), calculated from time spent in each state combined with health-state utility values. A one-way deterministic sensitivity analysis explored the impact of uncertainty in key model parameters on results, and probabilistic uncertainty was assessed through a Monte Carlo probabilistic sensitivity analysis.

RESULTS

Ribociclib plus letrozole was dominant versus palbociclib plus letrozole, with a cost saving of $43,037 and a gain of 0.086 QALYs. Compared with letrozole monotherapy, ribociclib plus letrozole was associated with an incremental cost of $144,915 and an incremental QALY of 0.689, equating to an incremental cost-effectiveness ratio of $210,369 per QALY. Key model drivers included OS HRs for palbociclib plus letrozole versus letrozole and for ribociclib plus letrozole versus letrozole, the PFS HR for palbociclib plus letrozole versus letrozole, PD health-state costs, utility of response, and cost discount rate. The probabilities that ribociclib plus letrozole was cost-effective versus letrozole at thresholds of $50,000, $100,000 and $200,000 per QALY gained were 1.6%, 6.3%, and 50.5%, respectively.

CONCLUSIONS

In the United States, ribociclib plus letrozole is a cost-effective alternative to palbociclib plus letrozole for the first-line treatment of postmenopausal women with HR+/HER2- advanced or metastatic breast cancer. Ribociclib plus letrozole is also cost-effective versus letrozole monotherapy at willingness-to-pay thresholds greater than $198,000 per QALY (for probabilistic analysis).

DISCLOSURES

Funding for this study was provided by Novartis, which manufactures ribociclib and provided input on the study design and data collection, analysis, and interpretation. Mistry, May, Suri, and Young are employees of PAREXEL. Tang, Mishra, D. Bhattacharyya, and Dalal are employees of Novartis. S. Bhattacharyya was an employee of Novartis during the study period. Tang and Dalal hold stock in Novartis. Brixner, Oderda, and Biskupiak were paid by Millcreek Outcomes Group as consultants for work on this project. Brixner has also consulted for AstraZeneca, UCB, Regeneron, and Abbott.

Role of cyclin-dependent kinase 4/6 inhibitors in the current and future eras of cancer treatment

Cyclin-dependent kinase 4/6 inhibitors, which act by inhibiting progression from the G1 to S phases of the cell cycle, include palbociclib, ribociclib, abemaciclib, and trilaciclib. Palbociclib and ribociclib are currently food and drug administration-approved for use in combination with aromatase inhibitors in postmenopausal women with metastatic hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer. Palbociclib is also food and drug administration-approved for use in combination with fulvestrant in hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer progressing after endocrine therapy. Abemaciclib is the newest cyclin-dependent kinase 4/6 inhibitor to gain Food and Drug Administration (FDA) approval, specifically as monotherapy for hormone receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer previously treated with chemotherapy and endocrine therapy. Abemaciclib also shares a similar indication with palbociclib for use in combination with fulvestrant in hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer progressing after endocrine therapy. Trilaciclib use remains largely investigational at this time. However, despite FDA-approval for only metastatic hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer, all four cyclin-dependent kinase 4/6 inhibitors have shown promise in hematologic malignancies and non-breast solid tumors. Although further research is needed, cyclin-dependent kinase 4/6 inhibitors represent intriguing developments in the treatment of various malignancies, including those with such poor prognoses as glioblastoma multiforme, mantle cell lymphoma, and metastatic melanoma. We discuss the approved indications, current research, and areas of future exploration for palbociclib, ribociclib, abemaciclib, and trilaciclib.

Palbociclib: A Review in HR-Positive, HER2-Negative, Advanced or Metastatic Breast Cancer

Oral palbociclib (Ibrance®) is a first-in-class, highly selective inhibitor of cyclin-dependent kinases 4 and 6 (i.e. a CDK4/6 inhibitor). It is indicated for the treatment of women with HR-positive, HER2-negative advanced or metastatic breast cancer, in combination with an aromatase inhibitor as initial endocrine-based therapy, and in combination with fulvestrant (with or without a luteinizing hormone-releasing hormone agonist) in those previously treated with endocrine therapy. In clinical trials, palbociclib in combination with letrozole as initial endocrine-based therapy in postmenopausal women (PALOMA-1 and PALOMA-2), or in combination with fulvestrant in pre-, peri-, or postmenopausal women with disease progression after endocrine therapy (PALOMA-3), significantly prolonged progression-free survival (PFS) and improved clinical benefit response (CBR) rates. Neutropenia was the most commonly reported any-grade and grade ≥ 3 adverse event. It was infrequently associated with febrile neutropenia (<2%) and generally manageable with a palbociclib dose delay, interruption or reduction, without the routine use of growth factors, and without affecting efficacy. In conclusion, oral palbociclib combination therapy is a valuable emerging option for use in patients with HR-positive, HER2-negative advanced or metastatic breast cancer.

Palbociclib in hormone receptor positive advanced breast cancer: A cost-utility analysis

INTRODUCTION

The addition of palbociclib to letrozole improves progression-free survival in the first-line treatment of hormone receptor positive advanced breast cancer (ABC). This study assesses the cost-utility of palbociclib from the Canadian healthcare payer perspective.

METHODS

A probabilistic discrete event simulation (DES) model was developed and parameterised with data from the PALOMA 1 and 2 trials and other sources. The incremental cost per quality-adjusted life-month (QALM) gained for palbociclib was calculated. A time horizon of 15 years was used in the base case with costs and effectiveness discounted at 5% annually. Time-to- progression and time-to-death were derived from a Weibull and exponential distribution. Expected costs were based on Ontario fees and other sources. Probabilistic sensitivity analyses were conducted to account for parameter uncertainty.

RESULTS

Compared to letrozole, the addition of palbociclib provided an additional 14.7 QALM at an incremental cost of $161,508. The resulting incremental cost-effectiveness ratio was $10,999/QALM gained. Assuming a willingness-to-pay (WTP) of $4167/QALM, the probability of palbociclib to be cost-effective was 0%. Cost-effectiveness acceptability curves derived from a probabilistic sensitivity analysis showed that at a WTP of $11,000/QALM gained, the probability of palbociclib to be cost-effective was 50%.

CONCLUSION

The addition of palbociclib to letrozole is unlikely to be cost-effective for the treatment of ABC from a Canadian healthcare perspective with its current price. While ABC patients derive a meaningful clinical benefit from palbociclib, considerations should be given to increase the WTP threshold and reduce the drug pricing, to render this strategy more affordable.

Progress with palbociclib in breast cancer: latest evidence and clinical considerations

Deregulation of the cell cycle is a hallmark of cancer, and research on cell cycle control has allowed identification of potential targets for anticancer treatment. Palbociclib is a selective inhibitor of the cyclin-dependent kinases 4 and 6 (CDK4/6), which are involved, with their coregulatory partners cyclin D, in the G1-S transition. Inhibition of this step halts cell cycle progression in cells in which the involved pathway, including the retinoblastoma protein (Rb) and the E2F family of transcription factors, is functioning, although having been deregulated. Among breast cancers, those with functioning cyclin D-CDK4/6-Rb-E2F are mainly hormone-receptor (HR) positive, with some HER2-positive and rare triple-negative cases. Deregulation results from genetic or otherwise occurring hyperactivation of molecules subtending cell cycle progression, or inactivation of cell cycle inhibitors. Based on results of randomized clinical trials, palbociclib was granted accelerated approval by the US Food and Drug Administration (FDA) for use in combination with letrozole as initial endocrine-based therapy for metastatic disease in postmenopausal women with HR-positive, HER2-negative breast cancer, and was approved for use in combination with fulvestrant in women with HR-positive, HER2-negative advanced breast cancer with disease progression following endocrine therapy. This review provides an update of the available knowledge on the cell cycle and its regulation, on the alterations in cyclin D-CDK4/6-Rb-E2F axis in breast cancer and their roles in endocrine resistance, on the preclinical activity of CDK4/6 inhibitors in breast cancer, both as monotherapy and as partners of combinatorial synergic treatments, and on the clinical development of palbociclib in breast cancer.