89Zr-RO5323441 PET Imaging in Glioblastoma

The research the investigators propose is a molecular imaging study of RO5323441, an antibody against placental growth factor (PlGF) in patients with recurrent GBM treated with bevacizumab, a drug against vascular endothelial growth factor (VEGF). Both VEGF and PlGF are molecules involved in tumor growth since they enable the development of tumor vasculature, thus delivery of oxygen and nutrients to the tumor. The treatment will consist of bevacizumab (i.v.) given every 2 weeks, until the patient has clinical benefit (no disease progression) or unacceptable toxicity. Meanwhile, patients will receive and injection of low protein-dose radiolabeled RO5323441 (89Zr-RO5323441) on day -3 and 11 of the first bevacizumab treatment cycle. Brain-only 89Zr-RO5323441 positron emission tomography (PET) will be performed at 2 hours after each injection of 89Zr-RO5323441 on day -3 and 11. Whole body 89Zr-RO5323441 PET will be performed on day 1 and 15, before and after the first treatment with bevacizumab. The main purpose of this trial is to determine how much of RO5323441 actually gets into the recurrent GBM lesions, since for a drug to be active, it has to be able to reach cancer cells. As second aims, RO5323441 accumulation in normal, non-tumor organs, will be assessed, as well as how bevacizumab influences RO5323441 penetration into tumor lesions (to answer the question of combined bevacizumab + RO5323441 treatment in GBM) or RO5323441 biodistribution in non-tumor organs.