Review of these GBM cases also revealed additional low frequency mutations in cancer genes that have been previously described to be altered in standard GBM (Table 3) including mutations in IDH1 (3; 4.8%), KRAS (1; 1.6%), PIK3CA (4; 6.5%), and TP53 (7; 11.3%) supporting the strength of using multiplexed tumor genotyping to identify low frequency mutations, some of which can be treated with targeted therapeutics. This evidence concerns the gene PIK3CA and glioblastoma.