Palbociclib plus aromatase inhibitors in patients with metastatic breast cancer and cardiovascular diseases: real-world effectiveness.

Background: Patients with cardiovascular disease (CVD) comorbidities are often excluded from participating in breast cancer clinical trials. Consequently, data to inform treatment decisions for patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer (mBC) and CVD are limited.

Objective: We compared the effectiveness of first-line palbociclib plus an aromatase inhibitor (AI) vs an AI alone and evaluated palbociclib treatment patterns in patients with HR+/HER2- mBC and CVD in routine clinical practice.

Methods: Data from the Flatiron Health Analytic Database were captured for patients with HR+/HER2- mBC and CVD who initiated first-line treatment with palbociclib plus an AI or an AI alone between February 2015 and March 2020 (data cutoff: September 30, 2020). Overall survival (OS), real-world progression-free survival (PFS), and treatment patterns were evaluated.

Results: Of the 469 patients with identifiable CVD, 160 received palbociclib plus an AI, and 309 received an AI alone. After stabilized inverse probability treatment weighting, both median OS (40.7 vs 26.5 months; hazard ratio [HR], 0.732 [95% CI, 0.537-0.997]; P = .048) and median real-world PFS (20.0 vs 12.5 months; HR, 0.679 [95% CI, 0.512-0.900]; P = .007) were significantly prolonged in patients treated with palbociclib plus an AI vs an AI alone. Among patients with a documented palbociclib starting dose, 78.5% started palbociclib at 125 mg/day, and 38.6% experienced dose adjustment.

Conclusions: In this real-world analysis, first-line palbociclib plus an AI was associated with improved effectiveness compared with an AI alone in patients with HR+/HER2- mBC and CVD.

Trial registration: NCT05361655 (ClinicalTrials.gov).