Background: Glioblastoma (GBM) is the most aggressive primary brain tumor in adults, with near-universal recurrence despite multimodality treatment. Increasing evidence suggests that the subventricular zone (SVZ), a major neural stem cell niche, may contribute to tumor aggressiveness, recurrence, and therapeutic resistance. However, the clinical significance of incidental SVZ irradiation remains controversial.
Methods: This prospective analytical study included 28 consecutive patients with histologically confirmed GBM treated uniformly with maximal safe resection followed by temozolomide-based chemoradiation using IMRT/VMAT. Ipsilateral, contralateral, and bilateral SVZs were retrospectively contoured, and dosimetric parameters were extracted. Survival outcomes were correlated with SVZ contact and radiation dose. The primary endpoints were overall survival (OS) and progression-free survival (PFS).
Results: With a median follow-up of 14.5 months, median OS and PFS were 13 months and 6.5 months, respectively. Tumors contacting the SVZ were associated with inferior OS (7 vs 15 months; p = 0.044) and shorter PFS. On univariate analysis, SVZ contact was associated with worse survival (HR 4.04). Among patients with SVZ-contacting tumors, a higher ipsilateral SVZ dose (≥52.14 Gy) showed a trend toward improved OS (p = 0.04). However, given the limited number of events, these findings should be interpreted with caution.
Conclusion: SVZ contact appears to identify a higher-risk subgroup of GBM patients. Higher incidental irradiation of the ipsilateral SVZ may be associated with improved survival; however, due to the small sample size and limited events, these findings are exploratory and hypothesis-generating. Larger prospective studies are required before clinical implementation.
Keywords: glioblasoma multiforme; glioblastoma; neural stem/progenitor cells; radiotherapy; subventricular zone.
Copyright © 2026 Pillai, Mehta, Parikh, Dash, Shivhare, Shah, Pandya, Singh, Prajapati, Bahuguna and Darji.