MacArthur et al described a telomerase-based assay to detect CTCs in peripheral blood samples of patients (8 of 11, 72%) with high-grade gliomas.73 Sullivan et al identified CTCs from blood samples in 13 of 33 (39.3%) patients with GBM using a microfluidic device that removes leukocytes from blood samples, enriching for CTCs without requiring tumor cell-specific capture antibodies.74 Sullivan et al also demonstrated that the frequency of CTCs with EGFR amplification was similar to the frequency of patient-matched tumor cells with EGFR amplification. This evidence concerns the gene EGFR and central nervous system cancer.