Effectiveness of Gamma Knife radiosurgery for recurrent glioblastoma: a 10-year retrospective analysis.

No standard treatment for recurrent glioblastoma (rGBM) has been established. However, Gamma Knife radiosurgery (GKRS) is considered a viable option for local control. We aimed to examine the clinical characteristics of patients treated with GKRS for rGBM at our institution over 10 years. We retrospectively analyzed data of 38 patients who underwent GKRS for rGBM from April 2012 to March 2022, all of whom had received standard first-line treatment before recurrence. Forty-eight GKRS sessions were conducted on the 38 patients (stereotactic radiosurgery [SRS], 40; stereotactic radiotherapy, 8). The median marginal dose for SRS was 18 (range, 12-22) Gy. The median patient age was 62 (28-83) years. As part of postoperative chemoradiotherapy, radiation doses were 35 Gy for 1 patient, 40 Gy for 10 patients, and 60 Gy for 27 patients. The median time from surgery to GKRS was 11 (2-44) months. Adverse radiation effects included radiation necrosis in five patients (13%) and cerebral edema in two (5%). Progression at the GKRS site was observed in 24 patients (63%), with a median time to progression of 4.5 months. The median overall survival was 20 months, and that after GKRS was 12 months. A longer interval from surgery to GKRS (multivariable) and a total postoperative radiation dose of 60 Gy (univariate) were significant prognostic factors. GKRS shows promise as a treatment for rGBM, particularly for patients with a longer interval before recurrence and those receiving a 60-Gy postoperative radiation dose.