PIK3CA and breast cancer: The results of SOLAR‐1 trial showed that breast cancer patients with hotspot mutations in the C2, helical, and kinase domains of PI3K (exons 7, 9, and 20) identified by the PCR‐based tool (therascreen PIK3CA RGQ PCR Kit), the US FDA‐approved CDx assay, exhibited superior clinical benefits from the combination therapy of alpelisib and fulvestrant.11