Multiple PIK3CA mutation clonality correlates with outcomes in taselisib + fulvestrant-treated ER+/HER2–, PIK3CA-mutated breast cancers

Mutations in the p110α catalytic subunit of phosphatidylinositol 3-kinase (PI3K), encoded by the PIK3CA gene, cause dysregulation of the PI3K pathway in 35–40% of patients with HR+/HER2– breast cancer.