Combination of palbociclib with adjuvant endocrine therapy for treatment of hormone receptor-positive and human epidermal growth factor receptor 2-negative metastatic breast cancer: An experience at two cancer centers in Saudi Arabia

The addition of palbociclib (a cyclin-dependent kinase 4/6 inhibitor) to endocrine therapy (ET) has been shown to significantly improve progression-free survival (PFS) and overall survival (OS) among patients with hormone receptor-positive (HR(+)) advanced breast cancer. The current study presents the local experience of using palbociclib at two cancer centers in Saudi Arabia. Electronic data of patients with metastatic HR(+) and human epidermal growth factor receptor 2-negative breast cancer who progressed after prior ET and received at least one cycle of palbociclib plus ET, were retrospectively reviewed. A total of 97 patients were identified, and their data were included in the analysis. The median age of the patients was 55 years. Patients were heavily pretreated in the metastatic setting (55% received systemic chemotherapy and 49% received two or more lines of prior ET). In total, 29 (30%) and 50 (52%) patients achieved an objective response and clinical benefit, respectively. The median follow-up time was 31.0 months [95% confidence interval (CI), 16.9-44.9] and the median PFS time was 16.3 months (95% CI, 11.4-21.2), with 58% of patients remaining progression-free at 12 months. Upon multivariate regression analysis, liver involvement was the only significant independent variable that predicted a greater risk of progression or death (hazard ratio, 2.32; 95% CI, 1.22-4.40; P=0.010). The median OS time was 19.6 months (95% CI, 18.1-20.9), with 12- and 24-month OS rates of 75 and 30%, respectively. Overall, real-world data showed that administration of palbociclib in combination with ET in patients with advanced HR(+) breast cancer achieved a favorable outcome that was comparable to that reported in clinical trials.