Reclassifying HER2-equivocal disease
To the Editor,
Based on repeat HER2 testing of a large series of invasive breast cancer cases, Xu et al. nicely demonstrated that significantly more tumors will be defined as HER2-positive based on the 2013 American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines compared to how those tumors would have been classified based on the 2007 ASCO/CAP guidelines .
The authors conclude that “Repeat HER2 testing clarifies HER2 status in about 50% of initial HER2 equivocal cases.” I do not believe “reclassification” should be conflated with “clarification.” Clarifying would imply that patients with tumors defined as HER2-positive based solely on one of the 2013 ASCO/CAP expanded definitions would have a significant potential of benefitting from anti-HER2 therapy, as do patients with tumors defined as HER2-positive based on the 2007 ASCO/CAP guidelines.
Reclassifying particular tumors as HER2-positive is not a clarification of status, but rather a change in status. As the authors acknowledge, the benefit of anti-HER2 therapy for patients with tumors defined as HER2- positive based solely on one of the 2013 ASCO/CAP expanded definitions remains unknown. Clinical trials are needed to determine the efficacy of anti-HER2 therapy for patients with tumors classified as HER2-positive based solely on the 2013 ASCO/SEP guidelines.
Compliance with ethical standards
Conflict of interest
There are no relevant conflicts of interest associated with this letter.