PIK3CA and breast cancer: Using cfDNA, they function as a companion diagnostic test for the following therapies: rucaparib (identifying BRCA1 and BRCA2 genes in patients with ovarian cancer), alectinib (anaplastic lymphoma kinase [ALK] rearrangements in non-small-cell lung cancer [NSCLC]), alpelisib (PIK3CA gene mutations in breast cancer), olaparib (mutations in BRCA1 and 2 and ATM genes in metastatic castration-resistant prostate cancer), and vitrakvi (NTRK fusions, location-agnostic).