A retrospective study of patients with ER+/PR+/HER2+ breast cancer showed that trastuzumab plus chemotherapy significantly prolonged recurrence-free survival (RFS) and breast cancer-specific survival (BCSS) compared with chemotherapy alone, but no significant survival benefit was obtained in the subgroup with > 50% expression of both ER and PR (12). This evidence concerns the gene ESR1 and breast carcinoma.