Radiosurgery for recurrent high-grade gliomas: a critical analysis based on a retrospective single-center series

The role of Stereotactic Radiosurgery (SRS) in the management of recurrent high-grade gliomas (rHGG) remains debatable, with no clear guidelines on when and how to incorporate it. Since 2012, Gamma Knife radiosurgery (GKRS) has been utilized in our institution in rHGG as a potential salvage modality. We present the rationale and outcomes of its use from a neuro-oncology referral center. A retrospective review of the medical records (2012-2023) was performed to identify 25 rHGG patients who were given GKRS that fulfilled the eligibility criteria. Eligibility was defined by a Karnofsky Performance Status (KPS) of at least 60, focal contrast-enhancing lesions that were treated in a single fraction, and/or ineligibility for surgery. Among 25 patients, most patients were male (72%) and any histological subtypes of glioblastoma vs. high-grade astrocytoma did not exhibit significant differences in terms of overall survival (OS; median 18.4 months vs. 14.4 months; p = 0.6091) or PFS (median 10.1 months vs. 4.3 months; p = 0.1557). Patients with a single lesion at GKRS had higher KPS scores at the time of radiosurgery (p = 0.0267), and number of lesions at radiosurgery moderately and negatively correlated with functional status (rs= -0.45514; p = 0.02909). Smaller lesion volume (less than 5 cc) at GKRS also correlated with significantly higher KPS (p = 0.0387) and also trended towards a longer OS (median 20.7 months vs. 6.4 months for ≥ 5 cc, p = 0.0531). Age of patients at GKRS was not significant for OS or PFS. This would suggest that diminishment in the extent of lesions translates to better functional activities without full restoration of neurologic deficits. GKRS confers a potential salvage role in the management of rHGG, particularly in patients who have limited disease burden and an intact performance status. While it showed correlation for lower lesion volume and fewer lesions with better KPS, the trend towards longer OS with smaller volume did not achieve statistical significance. Among the key limitations include small sample size, single-center retrospective study design, and uniform use of Bevacizumab. Therefore, larger, prospective, multicenter studies are essential to validate these trends, establish definitive survival benefits, and refine patient selection criteria.