In both arms, treatment repeats every 28 days for up to 24 courses in the absence of disease progression or unacceptable toxicity. All patients undergo MRI at baseline and at every 2 courses (no 2-week MRI) per standard of care until progression or discontinuation of treatment to assess areas of breakdown of the blood-brain barrier. Patients undergo an additional MRI after study therapy. Consenting patients also undergo diffusion and perfusion MRI and magnetic resonance spectroscopic imaging for correlative studies.