PIK3CA and breast cancer: While the therapy of patients with advanced BC was historically limited to chemo- and endocrine therapy with relatively poor outcomes, the therapeutic options now range from immune checkpoint inhibitors (ICIs) to poly ADP ribose polymerase (PARP), cyclin-dependent kinase (CDK) 4/6, mammalian target of rapamycin (mTOR), AKT, and phosphoinositide 3-kinase (PI3K) inhibitors.