After a CDK4/6 Inhibitor: State of the Art in Hormone Receptor-Positive Metastatic Breast Cancer

Area of Science:

• Oncology
• Pharmacology
• Genomics

Background:

• Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) are a cornerstone of first-line treatment for hormone receptor-positive metastatic breast cancer, improving progression-free and overall survival.
• Treatment resistance to CDK4/6i is inevitable, necessitating the exploration of subsequent therapeutic strategies.
• Tumor heterogeneity and specific resistance mechanisms, such as ESR1 and PIK3CA alterations, complicate treatment decisions post-CDK4/6i therapy.

Purpose of the Study:

• To review the current standards of care for hormone receptor-positive metastatic breast cancer following CDK4/6i progression.
• To explore emerging therapeutic options and combination strategies for patients who have progressed on CDK4/6i inhibitors.
• To highlight the role of molecular profiling and ongoing clinical trials in personalizing treatment approaches.

Main Methods:

• Review of current clinical practices and published literature on CDK4/6i therapy in metastatic breast cancer.
• Analysis of emerging therapeutic agents targeting resistance mechanisms, including novel endocrine agents, PI3K/AKT pathway inhibitors, and antibody-drug conjugates (ADCs).
• Discussion of the impact of genomic profiling in identifying actionable alterations and guiding treatment selection.

Main Results:

• CDK4/6i inhibitors demonstrate significant benefits in progression-free and overall survival for HR+, HER2- metastatic breast cancer.
• Diverse resistance mechanisms, including ESR1 and PIK3CA mutations, are identified as key challenges in the post-CDK4/6i setting.
• Novel agents and combination strategies show promise in biomarker-selected populations, offering new treatment avenues.

Conclusions:

• Optimal treatment sequencing after CDK4/6i progression remains an area of active investigation.
• Genomic profiling is crucial for understanding resistance mechanisms and guiding personalized therapy selection.
• Advances in novel endocrine agents, targeted therapies, and ADCs are reshaping the treatment landscape beyond CDK4/6i resistance, aiming to improve patient outcomes.