Patient P10 with breast cancer and a phosphoinositide-3-kinase catalytic alpha polypeptide (PIK3CA)_H1047R truncal mutation was enrolled into a highly selective PI3Kα/β inhibitor phase 1 (dose escalation) trial [16], but progressed shortly after with a PFS of 1.9 months and PFS ratio of 0.95 despite deriving symptomatic benefit while on the trial. This evidence concerns the gene PIK3CA and breast cancer.