Efficacy and safety of abemaciclib in combination with endocrine therapy for HR+/HER2- advanced or metastatic breast cancer: A systematic review and meta-analysis.

e13096 Background: Breast cancer, particularly the HR+/HER2- subtype, remains a major global health concern. Abemaciclib, a CDK4/6 inhibitor, has shown promise in treating advanced cases. This study comprehensively assesses the efficacy and safety of Abemaciclib in combination with endocrine therapy for HR+/HER2- advanced or metastatic breast cancer. Methods: Following PRISMA guidelines, a systematic review and meta-analysis were conducted. A thorough literature search spanning PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov identified 22 studies. Inclusion criteria encompassed RCTs and retrospective cohort studies reporting on Abemaciclib in approved doses, either as monotherapy or in combination. Outcome assessments included PFS, ORR, SE/AE, and OS. Quality assessment utilized ROB II and NOS tools. Results: Analysis of 22 studies involving 14,010 patients revealed that Abemaciclib significantly improved PFS and ORR, with a 47% and 46% reduction in risk, respectively. A noteworthy 24% reduction in the risk of death was observed in the Fulvestrant combination group. However, Abemaciclib increased the risk of SE/AE by 104% and 304% in the Fulvestrant and NSAI combinations, respectively. Conclusions: Abemaciclib, particularly in combination with Fulvestrant, emerges as an effective therapeutic option for HR+/HER2- advanced or metastatic breast cancer, improving PFS and OS. The higher toxicity profile warrants cautious use, especially in treatment-naïve patients. This review informs future research directions and offers insights for clinical decision-making in the evolving landscape of breast cancer treatment.