Evaluating CDK4/6 Inhibitor Therapy in Elderly Patients with Metastatic Hormone Receptor-Positive, HER2-Negative Breast Cancer: A Retrospective Real-World Multicenter Study

Simple Summary This study explores the effectiveness and safety of a common breast cancer treatment in elderly patients, a group often overlooked in clinical trials. Specifically, it focuses on using CDK4/6 inhibitors with hormone therapy for treating metastatic HR+/HER2- breast cancer in patients aged 70 and older. This research aims to understand how well this treatment works and how tolerable it is for this vulnerable population, which faces unique challenges due to age and other health conditions. The results of this study may provide valuable insights for clinicians, enabling more informed treatment decisions which optimize therapeutic outcomes and enhance the quality of life for elderly patients with breast cancer.Abstract Background: Metastatic HR+/HER2- breast cancer is commonly treated with CDK4/6 inhibitors in combination with endocrine therapy. However, the efficacy and safety of this approach in elderly patients (>= 70 years) remain unclear, particularly in the context of real-world clinical practice. This study aims to evaluate the clinical outcomes and tolerability of CDK4/6 inhibitor treatments in this fragile population, which is often under-represented in randomized clinical trials. Patients and methods: This retrospective multicenter study included elderly patients with metastatic HR+/HER2-negative breast cancer receiving first-line CDK4/6 inhibitors. The primary endpoint was progression-free survival (PFS). The secondary endpoints focused on the overall survival (OS), safety, and tolerability, considering variables such as tumor subtype, age, comorbidities, and treatment specifics. Results: The median PFS and OS were slightly lower than those reported in clinical trials, reflecting the inclusion of a more fragile population. The luminal B subtype was linked to a poorer PFS, while other factors like age, BMI, and ECOG status did not significantly affect the outcomes. A safety analysis indicated a higher incidence of grade 3 or higher toxicities, especially in frail patients, leading to dose reductions. Despite these challenges, CDK4/6 inhibitors were generally well-tolerated, allowing most patients to continue therapy. Conclusions: CDK4/6 inhibitors with endocrine therapy are effective in elderly patients with metastatic HR+/HER2- breast cancer, though careful management is crucial to balance efficacy and minimize adverse events.