EGFR and glioblastoma: 44/47 patients with recurrent TISF ctDNA samples, including GBM (n = 35), oligodendroglioma (n = 4), and astrocytoma (n = 5), including 25 cases of in situ recurrence, 18 cases of non‐in situ recurrence, and one case (P37) of pseudoprogression; EGFR is the most common mutated gene in rGBM, followed by NF1 (Figure 2C).