Prognostic Tests for Estrogen Receptor–Positive Breast Cancer: Need for Global Consideration and Further Evolution

The NSABP B-31 trial testing the efficacy of adjuvant trastuzumab was almost derailed right after launching because 18% of the enrolled patients were found to be ERBB2-negative (formerly HER2 or HER2/neu) on central review of the initial 104 patients.¹ This prompted international efforts to improve reliability of ERBB2 testing, eventually leading to American Society of Clinical Oncology/College of American Pathologists Guideline for HER2 Testing. Ironically, OncotypeDx owes its creation to this event.