P07.22.B IMPACT OF RESIDUAL TUMOR ON SURVIVAL IN PATIENTS WITH GLIOBLASTOMA: A RETROSPECTIVE COHORT FROM A BRAZILIAN TERTIARY CENTER

Abstract BACKGROUND The extent of surgical resection is widely recognized as one of the main prognostic factors in the treatment of glioblastoma. Nevertheless, the specific impact of residual tumor on overall survival and functional outcomes remains underexplored in Latin American populations, particularly in academic centers with limited resources. MATERIAL AND METHODS A retrospective cohort study was conducted including patients of all age groups diagnosed with glioblastoma and submitted to surgical resection between January 2020 and December 2024 at the Hospital das Clínicas, Ribeirão Preto Medical School - University of São Paulo (USP). The primary objective was to assess the correlation between the presence of residual tumor and overall survival. Residual tumor was determined through early postoperative MRI (≤72 hours) and/or surgical report. Overall survival was defined as the time from surgery to death or last follow-up. Clinical variables analyzed included age, presence of residual tumor, and survival time. Kaplan-Meier survival curves and Cox proportional hazards regression were used to evaluate the prognostic impact of residual disease. RESULTS A total of 82 patients were included; 62.2% presented with postoperative residual tumor. The median overall survival was significantly higher in the gross total resection group (17.84 months) compared to those with residual tumor (8.92 months; p < 0.05). The absence of residual tumor was also associated with better neurological outcomes at hospital discharge and a higher likelihood of completing adjuvant therapy. CONCLUSION The presence of residual tumor after glioblastoma resection is associated with worse overall survival and poorer functional outcomes. These findings support the relevance of maximal safe resection as a central strategy in glioblastoma treatment, even in settings with technological and infrastructural limitations. The results reinforce the need for institutional protocols that prioritize early imaging assessment, aggressive surgical planning, and structured oncological follow-up.