PIK3CA and neoplasm: When comparing according to tissue biopsy site, ctDNA alteration was numerically more concordant with metastatic site DNA than primary tumor DNA in these three genes (overall concordance [Kappa], 78% vs 65% [0.57 vs 0.17] for TP53; 100% vs 74% [1.00 vs 0.41] for KRAS; and 100% vs 87% [1.00 vs 0.45] for PIK3CA).