DISP-17. Recurrent Glioblastoma in Argentina: Bridging Global Standards with Local Realities

Abstract Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults. Its recurrent form lacks a standard second-line (2L) therapy. This study aimed to describe the therapies used and analyze their association with overall survival (OS) and progression-free survival (PFS). A retrospective cohort of 199 adult patients with GBM treated between 2008 and 2023 in Argentina (Hospital Italiano de Buenos Aires and Instituto de Oncología Ángel H. Roffo) was analyzed. Descriptive statistics and survival analyses (Kaplan-Meier, log-rank, and univariate/multivariate Cox regression) were applied. Median age was 60 years (56% male); 65% underwent initial surgery, 74% received chemotherapy, and 80% radiotherapy. IDH mutation was present in 11% and EGFR amplification in 22%. A total of 22% received 2L, associated with younger age, better initial clinical response, and lower overall mortality (p<0.001). Overall mortality was 69%, with median OS of 12.1 months (n=161; 95% CI: 10.0–14.2). Receiving 2L was associated with improved OS: 18.9 versus 10.4 months (p=0.003). Median PFS was 9.66 months (n=160; 95% CI: 8.04–11.28); for PFS-2L, median: 4.34 months (n=42; 95% CI: 2.52–6.16). Among Beva-based regimens (bevacizumab ± irinotecan) versus non-Beva therapies (carmustine, temozolomide rechallenge, reirradiation, reoperation), medians were 4.20 vs 6.24 months (log-rank p=0.032; not significant in Cox model, p=0.509). PFS-3L (n=9) was 1.94 months (95% CI: 1.85–2.03). In the multivariate model, receiving 2L reduced the risk of death by 62% (HR: 0.38; p=0.015). IDH mutation, age <60 years, and better initial clinical response were associated with improved OS (p<0.001), while EGFR amplification was associated with higher mortality (p=0.043). In conclusion, biomarkers and initial clinical response emerged as relevant prognostic factors. Although Beva-based therapies showed no clear benefit in PFS-2L, access to 2L treatment was associated with improved OS, highlighting the need to individualize therapeutic strategies in recurrent GBM.