Navigating HER2-Low Testing in Invasive Breast Cancer: Update Recommendations for Pathologists

Area of Science:

• Oncology
• Pathology
• Biomarker Research

Background:

• Accurate distinction between HER2-low and HER2-negative breast cancer is increasingly important.
• Novel antibody-drug conjugates (ADCs) demonstrate efficacy in HER2-low expressing breast cancer (BC).
• Current HER2 testing guidelines are dichotomous (positive/negative), not accounting for HER2-low expression.

Purpose of the Study:

• To review the evolution and updates of ASCO/CAP guidelines for HER2 testing in breast cancer.
• To highlight the significance of the emerging HER2-low concept and its implications for treatment.
• To present updated Mexican recommendations for HER2 status evaluation, incorporating the HER2-low classification.

Main Methods:

• Review of current ASCO/CAP guidelines and literature on HER2 testing.
• Analysis of the impact of novel ADCs on HER2-low breast cancer treatment strategies.
• Development of updated national recommendations for HER2 assessment in breast cancer.

Main Results:

• The HER2-low classification represents a significant advancement in breast cancer diagnostics.
• Standardization of HER2 testing is needed to accurately identify patients who may benefit from HER2-targeted therapies.
• Updated guidelines and national recommendations are essential for personalized medicine approaches.

Conclusions:

• Accurate HER2 status assessment, including the HER2-low category, is vital for effective breast cancer management.
• Adoption of standardized testing protocols and updated guidelines will improve patient outcomes.
• Pathologist commitment to theranostic biomarker quality is critical for optimal oncology care in Mexico and globally.