JL1022E: Overall survival with first-line palbociclib plus an aromatase inhibitor (AI) vs AI in metastatic breast cancer: A large real-world database analysis
Background Palbociclib (PB), the first clinically available oral CDK4/6 inhibitor, in combination with endocrine therapy has become standard of care for HR+/HER2– advanced/metastatic breast cancer (MBC). This study compared overall survival (OS) of MBC patients treated with first-line PB+AI vs AI alone in US routine clinical practices.
Methods We conducted a retrospective analysis of HR+/HER2– MBC patients in the Flatiron Health longitudinal database, representing more than 2.4 million actively treated cancer patients in the US. Between February 2015 and March 2020, 2888 postmenopausal MBC women and men aged ≥18 years started first-line PB+AI or AI therapy. Patients were evaluated from start of PB+AI or AI to September 2020, death, or last visit, whichever came first. Both stabilized inverse probability treatment weighting (sIPTW) and propensity score matching (PSM) statistical methods were used to balance patient characteristics.
Results Of the eligible patients (1324 with PB+AI and 1564 with AI), median age was 70.0 years, 67.8% were white, 34.8% had de novo MBC, 29.4% had lung or liver involvement, 38.7% had bone-only disease. Median OS in PB+AI vs AI was 53.4 (95%CI=48.7-58.6) vs 40.4 (95%CI=36.3-44.9) months (mo) (HR=0.67, 95%CI=0.60-0.76, p< .0001), respectively. After sIPTW, median OS was 49.1 mo (95%CI=45.2-57.7) for PB+AI vs 43.2 mo (95%CI=37.6-48.0) for AI (HR=0.76, 95%CI=0.65-0.87, p< .0001). After 1:1 PSM, median OS was 57.8 mo (95%CI=47.2—NR) with matched PB+AI vs 43.5 mo (95%CI=37.6-48.9) with matched AI (HR=0.72, 95%CI=0.62-0.83, p< .0001). Table presents key patient characteristics and OS results.
Conclusions This largest to date real-world comparative effectiveness study demonstrated that palbociclib +AI was significantly associated with prolonged overall survival vs AI alone, supporting first-line palbociclib plus AI as a standard of care for HR+/HER2– MBC patients.
