Preliminary investigation of 18F-FDG and 18F-FETNIM PET-CT applied in head and neck cancer patients undergoing biological intensity modulated radiotherapy

Abstract

Objective To evaluate the feasibility of using Fluorine-18 fluorodeoxyglucose (18F-FDG) and Fluorine-18 fluoroerythronitroimidazole (18 F-FETNIM) in positron emission tomography with computed tomography (PET-CT) to define biological target volume during the biological intensity modulated radiotherapy (BIMRT).Methods Twelve patients with pathologically confirmed head and neck cancer were scanned with CT simulation,18F-FDG PET-CT and 18F-FETNIM PET-CT respectively before treatment.Three gross target volumes,GTVCT,GTVFDG and GTVFETNIM,were delineated correspondingly with three modalities.The volumes of primary tumor (P-) and metastatic lymph nodes (N-),denoted as GTVP-cT,GTVN-cT,GTVP-FDG,GTVN-FDG,GTVP-FETNIM and GTVN-FETNIM,were compared respectively.Results Both primary tumor and metastatic lymph node of the 12 patients had 18F-FDG uptake,and the average maximal standard uptake values (SUVmax) were 12.3 ±5.5 and 5.1 ±2.8,respectively.Positive primary tumor 18F-FETNIM uptake was observed in 9 patients,yet only 5 of whom had positive 18F-FETNIM uptake in lymph node metastases.Three patients had no 18F-FETNIM uptake in the primary tumor,among whom 1 had positive 18F-FETNIM uptake in lymph node metastases.The volumes of GTVP-CT,GTVP-FDG and GTVP-F-ETNIM were (22.23 ± 12.11),(20.83 ± 11.59) and (1.98 ± 1.81) cm3,respectively.The volumes of GTVN-CT,GTVN-FDC and GTVN-FETNIM were (10.77 ± 8.87),(10.41 ± 8.61) and (0.61 ± 1.08) cm3,respectively.Compared to CT imaging,the volume differences of primary tumor and metastatic lymph nodes shown on 18F-FDG PET-CT imaging were statistically not significant.Compared with CT and 18F-FDG PET-CT,the corresponding volumes were significantly smaller at 18F-FETNIM PET-CT (P ＜0.01).Conclusions The study demonstrated that PET-CT imaging using different tracers may define subregions of the tumor for biological target volume delineation,which provides foundations for BIMRT. Key words: Head and neck cancer; 18F-FDG PET-CT; 18F-FETNIM PET-CT; Biological intensity modulated radiotherapy