Rationale: Glioblastomas (GBM) account for 70% of all gliomas (80% of all malignant brain and CNS tumors) and remain the most aggressive sub-type of glioma, with a particularly poor prognosis. Surgery aimed to complete resection is the first therapeutic modality, however, the infiltrative nature of the disease makes a complete resection nearly impossible. In a randomized, phase III EORTC-NCIC trial, overall survival in newly diagnosed glioblastoma patients treated with concomitant temozolomide and radiotherapy followed by 6 cycles of temozolomide was 27.2% (95% CI 22.2-32.5) at 2 years, 16.0% (12.0-20.6) at 3 years, 12.1% (8.5-16.4) at 4 years, and 9.8% (6.4-14.0) at 5 years, treatment which is now standard of care. Almost all GBM patients experience relapse and there is no one generally agreed standard of care in recurrent GBM. Vascular endothelial growth factor-A (VEGF-A), a central regulator of physiological and pathological angiogenesis, is considered to play a major angiogenic role in GBM. Bevacizumab, a humanized monoclonal antibody against VEGF-A, showed a 28%RR,a 43% 6-month PFS and provided a consistent clinical benefit in terms of both delayed progression and increased median overall survival over historical controls. This benefit is limited however, with the tumor eventually evading treatment by for example compensatory upregulation of angiogenic factors like placental growth factor (PlGF). Therefore, targeting PlGF could be a new strategy of tumor angiogenesis inhibition, complementary to VEGF(R) inhibition. In preclinical setting, inhibiting PlGF has shown to inhibit growth and metastasis of various tumors. Humanized monoclonal PlGF antibody RO5323441 was evaluated in phase I trials in healthy volunteers and in cancer patients; no Dose Limiting Toxicity (DLT) was found, thus no Maximum Tolerated Dose (MTD) defined. Stable disease was observed in 6/23 patients on different dose levels. A phase I/II study of bevacizumab in combination with RO5323441 is currently ongoing in patients with recurrent GBM (NCT01308684). However, the amount of RO5323441 to reach the recurrent GBM, and how this is affected by bevacizumab treatment, are yet unknown. This can be determined by repetitive measurement of RO5323441 tumor uptake with 89Zr-RO5323441 PET.

Objectives: The objectives of this study are to assess the penetration of RO532441 into recurrent GBM by 89Zr-RO5323441 PET imaging and to quantify its uptake, to visualize and quantify 89Zr-RO5323441 non-tumor organ distribution, and to measure the effect of bevacizumab treatment on 89Zr-RO5323441 uptake in recurrent GBM.

Study design: This is a single center, investigator driven, 89Zr-RO5323441 PET imaging and bio-distribution study in patients with recurrent GBM treated with bevacizumab. Bevacizumab at a dose of 10 mg/kg body weight i.v. in 90 min on day 1 is given every 2 weeks in cycles of 6 weeks. The treatment with bevacizumab will continue until documented disease progression, unacceptable toxicity, patient refusal or patient's best interest. 89Zr-RO5323441 will be administered i.v. at a tracer dose of 5 mg (37 MBq) on day -3 and on day 11 of cycle 1 of bevacizumab treatment. Four PET scans will be performed (2 brain only PET scans and 2 whole body PET scans). Brain only PET scans will be performed 2 hours after each 89Zr-RO5323441 administration on day -3 and day 11, and will take 10 minutes/ scan. Whole body PET scans will be performed 4 days after each 89Zr-RO5323441 administration (before dosing with bevacizumab on day 1 and day 15), and will take 50 minutes/ scan. 89Zr-RO5323441 uptake values in recurrent GBM lesions at baseline and day 15 will be compared to assess bevacizumab effect on tracer tumor uptake. The purpose of the two early brain-only PET scans after each 89Zr-RO5323441 injection is to identify whether changes in 89Zr-RO5323441 uptake in recurrent GBM lesions following treatment with bevacizumab can be solely attributed to an effect on blood volume/ vascular permeability, or rather indicate a possible modulation of placental growth factor (PlGF) level in the tumor tissue. The rationale for the whole body 89Zr-RO5323441 PET scans is to assess 89Zr-RO5323441 non-tumor organs distribution at baseline, as well as to evaluate the influence bevacizumab treatment could exert on 89Zr-RO5323441 non-tumor organs uptake. For 89Zr-RO5323441 pharmacokinetics, blood samples will be taken 1 hour after 89Zr-RO5323441 tracer injection on d-3 and d11, respectively together with the blood samples for hematology on d1 and d15 during the 1st cycle of bevacizumab treatment. The rationale for this is that performing both the 89Zr-RO5323441 PET scan data quantification and the assessment of the tracer's blood pharmacokinetics would enable us to better understand the specificity of 89Zr-RO5323441 uptake in recurrent GBM lesions. Patients will be assessed for bevacizumab treatment response by brain MRI every 6 weeks (i.e. every cycle) in the first 6 month and every 12 weeks thereafter, until documented progression using the updated RANO criteria. Treatment and tracer injection related side effects will be assessed according to the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE; version 4.0) for toxicity and adverse event reporting.

Main study parameters/ endpoints: 89Zr-RO5323441 tumor uptake and organ distribution will be scored visually and quantitatively. Standardized uptake value (SUV) and relative uptake value (RUV) will be determined and compared in the recurrent GBM lesions and in relevant tissues at baseline and day 15.

Nature and extent of the burden and risk associated with participation, benefit and group relatedness: Bevacizumab is registered in The Netherlands for use in metastasized colon and breast cancer, in lung cancer and in advanced renal cell carcinoma and has already been tested in GBM clinical trials. Bevacizumab is expected to have clinical benefit for patients enrolled in this study and similar safety profile compared to the other indications. RO5323441 monotherapy was well tolerated in patients with advanced malignant diseases. In this study, one patient will receive a low total protein dose of 10 mg RO5323441 (2X5mg) in the tracer and it is expected that RO5323441 will not enhance bevacizumab related side effects. The total radiation dose of 89Zr-RO5323441 for a patient participating in this study would be 36 mSv for women and 30 mSv for men. According to the investigators this radiation burden is justifiable in this patient group by the information that can be obtained in this study. Risk: exposure to 89Zr-RO5323441 PET scan-related radiation, possibility of allergic reaction to the protein in the tracer, possible side-effects of bevacizumab.