Figure 4.

Follow-up MRI showed tumor progression. All patients received serial MRI as the standard of care. As presented in the images and the illustrative flowchart, A1–E1 stand for a postoperative representative timepoint, at which we could not notice an obvious sign of tumor progression on the MRI scans, but at which we suspected tumor progression according to the comprehensive conditions of patients, then TISF was collected, in which tumor-specific ctDNA mutations were detected. 2–4 months later, as shown in the images A2–E2, definite radiologic sign of tumor recurrence appeared. This is interesting but we still presume that the simple signature of ctDNA-positive in TISF could not be a biomarker for early predicting the recurrence of glioma, because of the special location of TISF, which is at the local site of the tumor. The tumor progression should be determined by a specific genetic analysis.