Efficacy and safety of palbociclib plus endocrine therapy for patients with HR

Background: Palbociclib is the first cyclin dependent kinase 4/6 (CDK4/6) inhibitor approved in China to be combined with endocrine therapy (ET) for patients with hormone receptor-positive (HR Methods: This was an observational study of patients with HR Results: A total of 64 patients were enrolled in this study, and 54.7% of them received palbociclib plus ET as the first-line treatment for ABC. The median PFS was 21.6 months (95% CI: 11.2-32.0 months) after a median follow-up period of 13.8 months (95% CI: 11.9-15.7 months). The 6-month progression-free rate was 75.4%, and 48.9% of patients remained progression-free at 12 months. Overall, the ORR was 21.6% and the CBR was 76.5%. Patients with the molecular typing of Luminal A (P=0.035), a lower Ki67 level (P<0.001), sensitivity or acquired resistance to ET (P=0.003), less than 3 visceral metastases lesions (P=0.001), and those who received palbociclib plus ET as first-line or second-line of treatment for ABC (P=0.001) showed longer PFS. A total of 53.1% of patients had grade 3-4 adverse events (AEs), but only 4.7% of patients experienced permanent discontinuation of treatment due to intolerable AEs. Conclusions: The efficacy of palbociclib plus ET is worthy of recognition and the toxicity was acceptable in this study, which is similar to previously reported data from randomized clinical trials and other real-world evidence. Treatment for ABC using palbociclib plus ET should be recommended more widely in China due to the efficacy and safety.