FDG PET/CT images were acquired in all 20 patients, using a Gemini TF scanner (Philips Healthcare, Cleveland, OH, USA) before and during RT. The timing of scanning during RT ranged from the 3rd to 4th week of RT (median, 26 days from the start of RT). The PET/CT scanning methods used were as previously described [14 (link)]. The acquired PET/CT images were transferred to a dedicated workstation and analyzed using the vendor-provided software (The Extended Brilliance Workspace with Fusion Viewer, Philips Healthcare). The software of the workstation provided automatically delineated volume-of-interest (VOI) over the tumor using a threshold of 50% of maximum standardized uptake value (SUVmax) [15 (link)]. Metabolic tumor volume (MTV) was defined as those voxels having an SUV greater than 50% of the SUVmax. Total lesion glycolysis (TLG) was calculated by multiplying MTV by the mean standardized uptake value (SUVmean). SUV, MTV, and TLG were measured at the primary tumor site. There were 3 patients whose metabolic parameters were unmeasurable at the primary tumor site after neoadjuvant chemotherapy, and their PET/CT parameters were measured at the metastatic nodal sites. If the tumor could not be distinguished from the background, MTV was set as a single voxel with a volume of 0.1 cm3. SUV was assigned with a default value of 1.0, which was the minimum value [16 (link)].