A Comparative Analysis of Palbociclib and Ribociclib in Metastatic Hormone Receptor-Positive, HER2-Negative Breast Cancer: A Prospective mid term Follow-Up Study from an Indian Cohort

Introduction: Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, such as Palbociclib and Ribociclib, have significantly improved outcomes for patients with hormone receptor-positive, HER2-negative (HR+/HER2-) advanced breast cancer. Although clinical trials have established the efficacy of these agents globally, real-world data from India is limited. This study compares the clinical effectiveness and safety profiles of Palbociclib and Ribociclib in a cohort of Indian patients Materials and Methods: This prospective study included 60 patients with metastatic HR+/HER2- breast cancer treated at Army hospitals and research centers in India between 2020 and 2023. Progression-free survival (PFS), overall survival (OS), and safety profiles were analyzed to assess the real-world performance of Palbociclib and Ribociclib. Patients were treated with either Palbociclib or Ribociclib in combination with standard endocrine therapy. Results: Among the 60 patients, the median PFS was 39.40 months for the Palbociclib group and 42.93 months for the Ribociclib group (p = 0.26), indicating no statistically significant difference. The median OS was 41.98 months in the Palbociclib group and 45.51 months in the Ribociclib group (p = 0.15), with Ribociclib showing a slight but non-significant survival advantage. The most common adverse event was neutropenia, which occurred in 26% of patients receiving Palbociclib and 23% of patients on Ribociclib. Deranged liver function tests (LFTs) and fatigue were also reported in both groups. Conclusions: Palbociclib and Ribociclib demonstrated comparable efficacy and safety profiles in this Indian cohort. While no statistically significant differences in PFS or OS were observed, the data suggest a marginal survival benefit with Ribociclib. These findings underscore the importance of individualized treatment plans in HR+/HER2- breast cancer, taking into consideration patient-specific factors. Larger studies with longer follow-up are needed to further clarify the nuances between these two agents.