Survival Outcomes of Luminal Metastatic Breast Cancer Patients According to Changes in Molecular Subtype at Re-Biopsy: Insights from the GIM-13-AMBRA Study.

Introduction: The treatment of MBC patients is guided by receptor status, with re-biopsy at relapse recommended to reassess hormone receptor (HR) status. Various treatment options are available for HER2-veMBC, including CDK4/6 inhibitors, PARP inhibitors, and checkpoint inhibitors. The study highlights the importance of determining receptor subtype for guiding treatment choices. Patients and Methods: The GIM 13 AMBRA study is a longitudinal cohort study involving 42 centers in Italy. It includes data from 939 HER2- MBC patients enrolled between May 2015 and September 2020. The study analyzes the impact of HR expression changes on clinical outcomes using Kaplan-Meier survival curves and other statistical methods. Results: Among the 939 patients, 588 were rebiopsied at first relapse. The study found no significant differences in disease-free survival (DFS), progression-free survival (PFS), or overall survival (OS) between patients whose tumors changed molecular subtype and those who did not. However, post-progression survival from first-line treatment (PPS1) was different between the two groups. Discussion: The study confirms the phenomenon of receptor discordance between primary tumors and metastases. It emphasizes the need for re-biopsy in recurrent MBC to guide treatment strategies. The findings align with previous studies and highlight the importance of understanding receptor changes for improving patient outcomes. Conclusions: The GIM 13 AMBRA study provides valuable insights into the impact of molecular subtype changes on survival outcomes in Luminal MBC patients. It underscores the importance of re-biopsy and personalized treatment strategies in managing metastatic breast cancer.