PIK3CA MUTATION

PIK3CA Mutation — present in approximately 40% of HR-positive breast cancers, PIK3CA status determines eligibility for alpelisib, the first FDA-approved PI3K inhibitor for metastatic HR+ breast cancer.

Whole genome sequencing evaluates all PIK3CA hotspot mutations (H1047R, E545K, E542K) and rare variants, alongside germline PIK3CA variants causing PIK3CA-related overgrowth spectrum (PROS).

PIK3CA

About this condition

PIK3CA Mutation

PIK3CA encodes the p110α catalytic subunit of PI3Kα, a lipid kinase activating the PI3K/AKT/mTOR pathway. PIK3CA is one of the most frequently mutated oncogenes — found in ~40% of HR+/HER2- breast cancer, ~25% of endometrial cancer, ~20% of cervical and head/neck cancers.

Alpelisib (Piqray) was FDA-approved for PIK3CA-mutant HR+/HER2- metastatic breast cancer based on SOLAR-1 demonstrating significant PFS improvement. PIK3CA testing is now mandatory before second-line therapy. Capivasertib (Truqap, AKT inhibitor) is also approved for PIK3CA/AKT1/PTEN-altered HR+ breast cancer.

Germline PIK3CA variants cause PIK3CA-related overgrowth spectrum (PROS) — including MCAP syndrome and CLOVES syndrome. Alpelisib has been repurposed for PROS with dramatic improvement in overgrowth, representing a gene-targeted therapy spanning cancer and rare disease.

Alpelisib treats both PIK3CA-mutant breast cancer AND PIK3CA-related overgrowth syndrome — the same drug for the same gene across cancer and developmental conditions.

Gene locus: PIK3CA (3q26.32)

PIK3CA testing is mandatory for HR+ metastatic breast cancer treatment planning. Without it, 40% of eligible patients miss alpelisib. WGS captures all PIK3CA variants comprehensively.

Alpelisib doubles PFS in PIK3CA-mutant HR+ breast cancer — molecular testing identifies eligible patients

SOLAR-1 demonstrated alpelisib+fulvestrant significantly improved PFS vs. fulvestrant alone in PIK3CA-mutant HR+/HER2- metastatic breast cancer. Without testing, 40% of eligible patients never receive this targeted therapy.

Germline PIK3CA causes overgrowth spectrum — alpelisib treats both cancer and developmental overgrowth

Germline PIK3CA gain-of-function variants cause segmental overgrowth, vascular malformations, and epidermal nevi. Alpelisib produces dramatic improvement. WGS identifies both somatic and germline PIK3CA variants.

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