AbstractObjectives:Glioblastoma is a lethal disease in the elderly population. We aimed to evaluate disease and treatment outcomes in the oldest-old patients.Methods:Patients >80 years old with histologically confirmed glioblastoma treated between 2004 and 2009 were identified. We included patients managed with best supportive care (BSC), temozolomide (TMZ) alone, radiotherapy (RT) alone, or concomitantly with TMZ (CRT). Survival outcomes were analyzed using the Kaplan–Meier method.Results:Ultimately, 48 patients were analyzed. Median age and Eastern Cooperative Oncology Group (ECOG) Performance Status were 82 years and 2, respectively. The median Age-Adjusted Charlson Index (AAC) was 6. Gross total and subtotal resections were performed in 16.7% and 18.8% of patients, respectively. Biopsy followed by RT alone was the treatment modality for 23/48 (47.9%), while 17/48 (35.4%) received surgery followed by RT alone or CRT. A total of 8 (16.7%) were managed with BSC after biopsy. Median overall survival (OS) and progression-free survival (PFS) were 4.1 (95% confidence interval [95% CI] 3.3-4.9) and 2.7 (95% CI 1.5-3.9) months, respectively. Improved median OS was observed in those treated with surgical resection followed by RT alone or CRT (7.1 months), compared to biopsy followed by RT alone (4.2 months) or BSC (2.0 months;p=0.002). Surgical resection, age≤85, and AAC<6 were associated with better OS (p=0.032,p=0.031, andp=0.02, respectively). Cause of death was neurological progression in 56% of cases. RT was well-tolerated.Conclusions:PFS and OS outcomes remain poor in the oldest-old patients (>80 years old). Younger age, lower AAC, surgical resection, and adjuvant treatment were associated with improved OS.