MGMT and neoplasm: Among 5 seropositive patients, the anti‐MGMT‐02 autoantibody peptide level decreased 30 days after surgery; 4 out of the 5 seropositive patients became seronegative, 5 patients with anti‐MGMT‐02 peptide autoantibodies reached preoperative levels again when tumor recurrence developed (Figure 5A).