Real-World Treatment Patterns and Outcomes of Palbociclib Plus an Aromatase Inhibitor for Metastatic Breast Cancer: Flatiron Database Analysis.

ABSTRACT

INTRODUCTION: To describe real-world treatment patterns and effectiveness of first-line palbociclib plus an aromatase inhibitor (PAL+AI) and examine the association between PAL initial dose and effectiveness among patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic/advanced breast cancer (HR+/HER2- MBC) in routine clinical practice. PATIENTS AND METHODS: This retrospective analysis used Flatiron Health's database of electronic health records from >280 cancer clinics representing >2.4 million actively treated cancer patients in the United States. Women with HR+/HER2- MBC who received first-line PAL+AI were included. Real-world progression-free survival (rwPFS) was defined as the time from starting PAL+AI to death or disease progression. Real-world best tumor response (rwBTR) was assessed based on the treating clinician's assessment of radiologic evidence for change in disease burden. RESULTS: Of 813 eligible patients, median age was 65.0 years, and median follow-up was 21.0 months. PAL was initiated at 125 mg/d and 75/100 mg/d in 86.5% and 13.5% of patients, respectively. Median duration of PAL+AI was 16.3 months. 43.0% of patients discontinued PAL+ AI; 11.0% discontinued because of toxicity. Median time to subsequent therapy and chemotherapy was 24.6 and 36.6 months, respectively. Median rwPFS was 20.0 months, and best rwBTR rate was 51.9%. Patients starting PAL at 125 versus 75/100 mg/d had longer median rwPFS (27.8 vs. 18.6 months) and higher rwBTR rate (54.0% vs. 40.4%). CONCLUSION: These data demonstrate the benefit of PAL+AI in routine clinical practice and may support the initiation of palbociclib at the recommended dose of 125 mg/d for HR+/HER2- MBC. TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION NCT04176354, November 25, 2019.