Bevacizumab can be an effective treatment for individuals with NF2 and improve different nerve functions (like hearing, tinnitus or balance problems) and the quality of life of NF2 patients. However, bevacizumab is not effective in all patients or all tumors, at the cost of moderate toxicity and considerable financial burden. Therefore, this observational study will validate an imaging biomarker method to predict bevacizumab efficacy in order to avoid adverse effects and high costs in non-responders to bevacizumab treatment. Patients will undergo standard-of-care treatment with the sole addition of a pre-treatment 89Zr-Bevacizumab PET/CT-scan. Per standard-of-care bevacizumab therapy is administered every three weeks for six months. To monitor treatment effect, follow-up is performed at 3-month intervals.