PIK3CA and breast cancer: Clinical trials, including GeparQuattro,7 GeparQuinto,8 GeparSixto,9 NeoALTTO10 and CHERLOB,11 all demonstrated that tumours harbouring a PIK3CA mutation were significantly associated with a lower pathological complete response (pCR) rate than those with wild‐type PIK3CA in the neoadjuvant cohort12, 13 and that the mutations were related to poor treatment efficacy in advanced breast cancer.14, 15