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

Abstract

AbstractThere 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.