Based on the fraction of IDHwt GBM samples in our cohort falling below the VAF/cellularity cutoffs identified by Cutoff Finder and regression (4.3% and 12.6%, respectively) and the known frequency of MGMT promoter methylation in IDH-wildtype GBM of ~ 35% [55], we estimate that 1.5-4.4% of IDHwt GBM MGMT pyrosequencing samples may have false-negative results, potentially impacting TMZ treatment decisions. Here, MGMT is linked to glioblastoma.