PIK3CA and breast cancer: Although clinical exploitation of PI3K pathway aberrations, most notably PIK3CA-mutation status, has since proven to be successful in selecting advanced breast cancer patients for treatment with the PI3K alpha-selective inhibitor alpelisib [19] and the AKT inhibitor capivasertib [22] in combination with fulvestrant, elucidation of novel patient-selection approaches in solid-tumor patients remains challenging.