Stereotactic Radiosurgery Versus Reoperation in Small Surgically Accessible Recurrent Glioblastoma

BACKGROUND AND OBJECTIVES: Even with multimodal therapy, glioblastoma invariably recurs. Reirradiation with stereotactic radiosurgery (SRS) and reoperation are frequent salvage treatment options for recurrent glioblastoma (rGBM) isocitrate dehydrogenase-wildtype. No study has compared the safety and efficacy of these treatments in a homogeneous rGBM population. In this study, we evaluate gamma knife (GK)-SRS vs reoperation in rGBM. METHODS: This retrospective study evaluated surgically accessible rGBM between 2005 and 2022. All patients received adjuvant radiotherapy and were evaluated for GK-SRS or reoperation on recurrence. Cox multivariable analysis and propensity-score matching were performed to address confounders in outcomes. Post-recurrence survival (PRS) was the primary endpoint. RESULTS: We identified 119 patients. Among these, 38 underwent GK-SRS and 81 underwent reoperation. Although patients undergoing GK-SRS had improved PRS and overall survival compared with reoperation, they had significant differences in baseline characteristics, particularly in tumor volume (reoperation group: 8.7 cm3 [IQR = 3.4-17.8 cm3] vs GK-SRS 1.7 cm3 [IQR = 0.2-6 cm3], P < .001). Given these significant differences, a propensity-score matching accounting for tumor volume and Karnofsky performance status was performed, comparing patients in which equipoise between GK-SRS and resection existed (GK-SRS 2.5 cm3 vs reoperation 2.6 cm3 and Karnofsky performance status 80 for both). Among these patients (23 in each group), PRS (19.2 months vs 15.1 months, P = .617) and overall survival (31.9 months vs 25.5 months, P = .176) were similar. Nevertheless, complications remained higher in the reoperation group (26.1% vs 4.3%, P = .040). CONCLUSION: In patients with small, surgically accessible first recurrent glioblastoma, GK-SRS achieved survival outcomes comparable to reoperation after matching for key baseline differences, while demonstrating a lower complication rate. These findings support GK-SRS as a reasonable local salvage option in carefully selected low-volume recurrences.