Effects of intermittent discontinuation cyclin-dependent kinase inhibitors on metastatic breast cancer during Lebanon's economic crisis.

Introduction: This study examines the intermittent discontinuation of palbociclib based on its availability and its clinical outcomes during the Lebanese economic crisis in patients with metastatic Breast Cancer (BC) HR+ between the years 2019 and 2023.

Methods: This study carries out a retrospective analysis on 46 patients treated with palbociclib - Letrozole during the years 2019 and 2023 in Lebanon. It used descriptive tables and figures to summarize demographic, clinical, and outcome characteristics. It analyzed the data using Student T test for parametric variables, Wilcoxon and Kruskal-Wallis tests for non-parametric variables, and Chi-squared and Fisher tests for qualitative variables. Pearson's correlation and regression models were used to associate between the intermittent administration of palbociclib and its clinical outcomes.

Results: Our sample had a mean age of 59.33 +/-13.27 years. 87% had ductal carcinomas and 13% had lobular carcinomas. 52.2% of patients had treatment for their metastases prior to palbociclib, and a discontinuation was observed in 63.1 %. Intermittent discontinuation is associated with advanced age (p=0.048) and statistically reduces PFS (p=0.026). The intermittent drug intake also affects PFS (p=0.03) but has no effect on the disease progression.

Conclusion: This study is the only research in the world focused on intermittent intake of palbociclib. The intermittent discontinuation of palbociclib is influenced by age and affects the PFS. These results highlight the significance of adherence and protocol compliance.