An Overview of Clinical Development of Agents for Metastatic or Advanced Breast Cancer Without ERBB2 Amplification (HER2-Low).

This review suggests that ERBB2-low may be a distinct, clinically relevant breast cancer entity warranting reassessment of traditional diagnostic and therapeutic paradigms. Ongoing clinical trials and further investigations may provide optimized strategies for diagnosing and treating ERBB2-low breast cancer, including reproducible, consistent definitions to identify patients in this diagnostic category and demonstration of benefits of emerging therapies.