Efficacy of palbociclib plus fulvestrant after everolimus in hormone receptor-positive metastatic breast cancer.

BACKGROUND: Palbociclib, a CDK4-6 inhibitor, combined with endocrine therapy (ET) is a new standard of treatment for Hormone Receptor-positive Metastatic Breast Cancer. We present the first real-life efficacy and tolerance data of palbociclib plus fulvestrant in this population.

METHODS: From November 2015 to November 2016, patients receiving in our institution palbociclib + fulvestrant according to the Temporary Authorization for Use were prospectively analyzed.

RESULTS: 60 patients were treated accordingly; median age was 61 years; 50 patients (83.3%) had visceral metastasis, and 10 (16.7%) had bone-only disease. Patients had previously received a median of 5 (1-14) lines of treatment, including ET (median 3) and chemotherapy (median 2); 28 (46.7%) received previously fulvestrant and all everolimus. With a median follow-up of 10.3 months, median progression-free survival (mPFS) was 5.8 months (95% CI 3.9-7.3). Patients pretreated with fulvestrant had a similar PFS of 6.4 months (HR 1.00; 95% CI 0.55-1.83; P = 1.00). The most common AEs (adverse events) were neutropenia (93%), anemia (65%), and thrombocytopenia (55%).

CONCLUSION: In this heavily pretreated population including everolimus, fulvestrant plus palbociclib provides an mPFS of 5.8 months with the same magnitude of benefit for fulvestrant-pretreated patients.