- Progressive enhancement (> 25% increase in contrast enhancing volume compared to nadir) on MRI within 14 days of registration, >= 42 days since completion of radiation/temozolomide therapy, and >= 28 days since surgical resection or cytotoxic chemotherapy; measurable enhancement is defined as two perpendicular in-plane diameters of at least 10 mm and at least 10 mm in the 3rd orthogonal direction