IDH1 and central nervous system cancer: One example was with patient 67, a 64-year-old man with IDH-mutant-noncodel glioma; after the second period of adjuvant TMZ treatment, five low-VAF (<0.8%) variants were detected in his first cf-tDNA sample without imaging findings, while 5 months later, 24 mutations with elevated VAFs (the maximal 49.3%) emerged in the relapsed cf-tDNA sample, wherein some were not found in the initial tumor tissue (Figure 2B).