Triplet Therapy for Bad-Acting ER+ Breast Cancer

The typical first-line treatment for ER+/HER2− metastatic breast cancer — an endocrine agent combined with a CDK4/6 inhibitor — affords a progression-free survival (PFS) benefit over endocrine therapy alone, but the magnitude of benefit appears to be smaller in the roughly 40% of patients whose tumors harbor PIK3CA mutations. For patients with PIK3CA mutations and disease progression in the first-line setting, combining fulvestrant with either a PI3K inhibitor or an AKT pathway inhibitor for the next treatment provides longer PFS than endocrine therapy alone. Based on these findings, investigators examined whether combining endocrine therapy with a CDK4/6 inhibitor and a PI3K inhibitor could improve outcomes in patients with these more-aggr…