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.

Real-World Tumor Response of Palbociclib Plus Letrozole Versus Letrozole for Metastatic Breast Cancer in US Clinical Practice

BACKGROUND

Limited information exists regarding tumor response to palbociclib plus an aromatase inhibitor (AI) versus AI alone in real-world practice.

OBJECTIVE

To evaluate the real-world tumor response of palbociclib plus letrozole (PAL+LET) versus LET alone as first-line treatment for patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer (HR+/HER2‒ MBC) in routine US clinical practice.

PATIENTS AND METHODS

This retrospective analysis included HR+/HER2‒ MBC patients who initiated PAL+LET or LET as first-line treatment between February 2015 and September 2018 in the Flatiron Health Analytics database. Patients were followed until December 2018. Real-world best tumor response (rwBTR) was determined based on physicians' assessment of radiologic evidence for change in burden of disease.

RESULTS

Of the 1383 eligible patients who initiated PAL+LET or LET as first-line therapy in the Flatiron database, 968 patients had ≥ 1 tumor response assessment (662 received PAL+LET and 306 received LET). The rwBTR rate (complete response+partial response) in the first-line setting was 59.8% in the PAL+LET group and 39.2% in the LET group (odds ratio 2.31 (95% CI 1.75‒3.04), P < 0.0001). After 1:1 propensity-score matching, the rwBTR rate was 58.6% in the PAL+LET group versus 39.1% in the LET group (odds ratio 2.21 (95% CI 1.50‒3.25), P < 0.0001).

CONCLUSIONS

This real-world analysis demonstrated that HR+/HER2‒ MBC patients were more likely to respond to PAL+LET compared to LET. These findings further showed the effectiveness of PAL+LET therapy in the real-world setting and support the combination as a standard of care for MBC.

STUDY REGISTRATION

Pfizer; NCT04176354; registered November 25, 2019.

CDK4/6 inhibitors in HR+/HER2- advanced/metastatic breast cancer: a systematic literature review of real-world evidence studies

Background: This review aims to qualitatively summarize the published real-world evidence (RWE) for CDK4/6 inhibitors (CDK4/6i) approved for treating HR+, HER2-negative advanced/metastatic breast cancer (HR+/HER2- a/mBC). Materials & methods: A systematic literature review was conducted to identify RWE studies of CDK4/6i in HR+/HER2- a/mBC published from 2015 to 2019. Results: This review identified 114 studies, of which 85 were only presented at scientific conferences. Most RWE studies investigated palbociclib and demonstrated improved outcomes. There are limited long-term and comparative data between CDK4/6i and endocrine monotherapy, and within the CDK4/6i class. Conclusion: Available RWE suggests that CDK4/6i are associated with improved outcomes in HR+/HER2- a/mBC, although additional studies with longer follow-up periods are needed.