PIK3CA and cancer: There is some evidence that TNBCs that express the AR (i.e., AR+) are less sensitive to chemotherapy but can respond to AR antagonists.2 Six-month clinical benefit rates of 19% and 29% in metastatic AR+ TNBC have been reported with bicalutamide (TBCRC 011) and enzalutamide, respectively.5,6 A higher frequency of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) mutations has also been reported in the AR+ compared with other subtypes of TNBC suggesting another potential therapeutic strategy for these cancers.7