The Adjuvant Paclitaxel and Trastuzumab (APT) trial was an open-label, single-arm, multicentre, phase 2 study that demonstrated the efficacy and safety of adjuvant paclitaxel and trastuzumab for node-negative, HER2+ breast cancer, with tumours ≤3 cm [15]. This evidence concerns the gene ERBB2 and breast cancer.