Gross Tumor Delineation in Esophageal Cancer on MRI Compared With 18F-FDG-PET/CT

摘要

PurposeCurrent delineation of the gross tumor volume (GTV) in esophageal cancer relies on computed tomography (CT) and combination with18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). There is increasing interest in integrating magnetic resonance imaging (MRI) in radiation treatment, which can potentially obviate CT- or FDG-PET/CT–based delineation. The aim of this study is to evaluate the feasibility of target delineation on T2-weighted (T2W) MRI and T2W including diffusion-weighted MRI (T2W?+?DW-MRI) compared with current-practice FDG-PET/CT.MethodsTen observers delineated primary esophageal tumor GTVs of 6 patients on FDG-PET/CT, T2W-MRI, and T2W?+?DW-MRI. GTVs, generalized conformity indices, in-slice delineation variation (root mean square), and standard deviations in the position of the most cranial and caudal delineated slice were calculated.ResultsDelineations on MRI showed smaller GTVs compared with FDG-PET/CT–based delineations. The main variation was seen at the cranial and caudal border. No differences were observed in conformity indices (FDG-PET/CT, 0.68; T2W-MRI, 0.66; T2W?+?DW-MRI, 0.68) and in-slice variation (root mean square, 0.13?cm on FDG-PET/CT; 0.10?cm on T2W-MRI; 0.14?cm on T2W?+?DW-MRI). In the 2 tumors involving the gastroesophageal junction, addition of DW-MRI to T2W-MRI significantly decreased caudal border variation.ConclusionsMRI-based target delineation of the esophageal tumor is feasible with interobserver variability comparable to that with FDG-PET/CT, despite limited experience with delineation on MRI. Most variation was seen at cranial-caudal borders, and addition of DW-MRI to T2W-MRI may reduce caudal delineation variation of gastroesophageal junction tumors.