Tumor Hypoxia Detected by 18F-fluoromisonidazole Positron Emission Tomography (FMISO PET) as a Prognostic Indicator of Radiotherapy (RT)

18F-misonidazole positron emission tomography (FMISO PET)/computed tomography (CT) obtained before and during radiotherapy (RT) was analyzed as to whether it could predict clinical outcome.Twenty-two patients were included. FMISO PET/ CT was performed twice before RT and at a dose of approximately 20 Gy/10 fractions. FMISO maximum standardized uptake values (SUVmax), the tumor-to-muscle ratios (T/M), and hypoxic volume (HV) in gross target volumes were measured.Of the 22 tumors, 18 had hypoxic areas (SUVmax ≥1.60) before RT. SUVmax, T/M, and HV on the first PET/CT were significantly correlated with initial tumor response, although the values during RT were not related to the response. The overall survival and loco-regional control rates of patients below cut-off values were significantly better than those above the cut-off values.Tumor hypoxia detected by FMISO PET/CT before RT may predict clinical outcome.