ERBB2 and neoplasm: In the Neoadjuvant Lapatinib and/or Trastuzumab Treatment Optimization Trial (NeoALTTO), tumours with PIK3CA mutations had lower pCR rates after treatment with neoadjuvant paclitaxel plus HER2-targeted therapy, with pCR rates decreasing from 34.5% in PIK3CA WT tumours to 21.3% in mutated tumours [32].