*3.7. 18F-FAZA*

One of the reasons leading to an increased metabolic activity detected with 18F-FDG PET/CT is tumor hypoxia. Tumor hypoxia leads to enhanced production of several hypoxia inducible factors, resulting in increased microvessel density (MVD) around the malignant plasma cells [6]. MVD has been proven to be correlated with disease progression in MM [87]. Based on this approach, de Waal et al. applied the PET tracer 1-α-D: -(5-deoxy-5-[18F]-fluoroarabinofuranosyl)-2-nitroimidazole ( 18F-FAZA), which accumulates in tumor hypoxia. The authors studied 5 patients with relapsed MM with 18F-FDG PET and 18F-FAZA PET. Although all patients had a positive 18F-FDG PET scan, no lesions were demonstrated on 18F-FAZA PET, reflecting a limited performance of this tracer in the workup of MM patients [88].
