The addition of palbociclib to fulvestrant was associated with significant and consistent improvement in progression-free survival compared with fulvestrant alone in patients with recurrent hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer, a study published in the journal The Lancet Oncology has shown.1
For the multicenter, double-blind, phase 3 trial, researchers enrolled 521 patients with HR-positive, HER2-negative metastatic breast cancer who had progressed on previous endocrine therapy. All patients had experienced disease relapse or progression after previous endocrine therapy for advanced disease during treatment or within 12 months of completion of adjuvant therapy.
Participants were randomly assigned 2:1 to receive fulvestrant 500 mg via intramuscular injection on days 1 and 15 of cycle 1 and on day 1 of subsequent 28-day cycles plus palbociclib 125 mg orally daily for 3 weeks of each 28-day cycle or placebo.
Results showed that median progression-free survival was 9.5 months (95% CI: 9.2-11.0) with palbociclib compared with 4.6 months (95% CI: 3.5-5.6) with placebo after a median follow-up of 8.9 months (HR, 0.46; 95% CI: 0.36-0.59; P<.0001).
Researchers found that this improvement in progression-free survival was observed regardless of the degree of endocrine resistance, HR expression level, or PIK3CA mutational status.
In terms of safety, the most common grade 3 or 4 adverse events in the fulvestrant plus palbociclib arm were neutropenia, leukopenia, and anemia. A total of 13% of the 345 patients in the combination arm experienced serious adverse events vs 17% of the 172 patients in the placebo group.
1. Cristofanilli M, Turner NC, Bondarenko I, et al. Fulvestrant plus palbociclib versus fulvestrant plus placebo for treatment of hormone-receptor-positive, HER2-negative metastatic breast cancer that progressed on previous endocrine therapy (PALOMA-3): final analysis of the multicentre, double-blind, phase 3 randomised controlled trial [published online ahead of print March 3, 2016]. Lancet Oncol. doi:10.1016/S1470-2045(15)00613-0.