To confirm these results and investigate short- and long-term side effects, cost-effectiveness, and quality of life, an international multicentre randomised controlled trial was initiated (SUBITO trial; NCT02810743) in which patients with stage III HER2-negative breast cancer were randomised to either HDCT or the Dutch standard of care plus a poly (ADP-ribose) polymerase (PARP) inhibitor (i.e. olaparib). This evidence concerns the gene ERBB2 and breast cancer.