- Diagnosis Patients with the histological diagnosis of recurrent GBM made either by biopsy or resection of recurrent disease. Cytological evidence of malignant cells in CSF and/or clinical and radiographic evidence of leptomeningeal disease are irrelevant in terms of inclusion or exclusion into this study. Bihemispheric extension ("butterfly GBM"), multi-focality, and/or subependymal spread are not contraindications to enrollment.