Insular Glioblastoma in the Elderly: Prognostic Factors and the Impact of Bevacizumab on Survival Outcomes

Introduction: Insular glioblastoma (GBM) presents unique therapeutic challenges due to its proximity to critical brain areas, limiting extent of resection with higher neurological risks. While maximal safe resection is known to improve survival in GBM patients, outcomes for elderly patients (>65 years) with insular GBM remain understudied. Our study seeks to identify prognostic factors and treatment outcomes in this population, addressing a key gap in neurosurgical oncology.

Methods: Retrospective review of newly diagnosed insular GBM patients that underwent craniotomies at our institution (2005-2022).

Results: In a cohort of 80 insular GBM patients, 37.5% were elderly (>65 years), with a median age of 69. Despite similar clinical characteristics and treatments between young and elderly groups, post-progression survival(PPS) was notably shorter in the elderly (2.9 versus 9.4 months, p=0.09). Across all patients, factors associated with poor survival were CAD (HR 2.40[1.12-5.14], p=0.023) and age>65 (HR 2.02[1.18-3.46], p=0.01), while improved survival outcomes were associated with postop KPS>80 (HR 0.35[0.15-0.82],p=0.016), adjuvant chemoradiation(HR 0.46[0.24-0.87], p=0.019), reoperation(HR 0.48[0.26-0.88], p=0.019), and salvage-bevacizumab (HR 0.45[0.21-0.96], p=0.041]). In the elderly, higher postoperative KPS (HR 0.08[0.01-0.62], p=0.016) and salvage-bevacizumab (HR 0.45[0.21-0.96, p=0.041]) significantly improved survival. Notably, elderly receiving salvage bevacizumab showed markedly increased PPS (9.5 vs 1.7 months, p=0.001) and OS (20.7 vs 8.9 months, p=0.03).

Conclusion : Elderly patients with insular GBM demonstrate comparable clinical outcomes to younger counterparts following surgery, with similar OS and PFS. However, PPS is significantly shorter in the elderly, likely due to age-related factors. Higher postoperative-KPS and salvage bevacizumab administration emerge as key factors associated with improved survival in this group. Notably, salvage bevacizumab significantly enhances all survival metrics in elderly patients, highlighting its critical role at recurrence. These findings warrant larger prospective studies to optimize treatment strategies for this complex patient population, potentially improving both quality of care and survival outcomes.