A post-hoc analysis of a large trial (the N4+ study, NCT03087409) has found a much larger reduction in disease recurrence by high-dose, alkylating chemotherapy for the subgroup of stage III, HER2-negative breast cancer patients with so-called BRCA1-like tumors (hazard rate (HR) 0.12) compared to non-BRCA1-like tumors (HR 0.78)5. This evidence concerns the gene ERBB2 and breast cancer.