Metabolic Tumor Burden From¹⁸F-FDG PET/CT Images As An Independent Prognostic Factor In Post-surgical Males With Squamous Esophageal Cancer

Objective To determine an optimal threshold method for the segmentation of metastaticlesions from18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computertomography (PET/CT) images, and evaluate18F-FDG PET/CT metabolic tumor burden withthis threshold as a post-surgical predictor of prognosis in males with esophageal squamouscell carcinoma.Methods18F-FDG PET/CT scanning was performed for post-surgical evaluation of34patients with esophageal squamous cell carcinoma, with each visible lesion delineated bythree thresholds, Thbgd20,Th40and Th2.5, using3D-area growing algorithms. The numbers oflesions in each patient successfully segmented by the three thresholds were compared, withwhole body total lesion glycolysis (WBTLG) calculated as the total lesion glycolysis (TLG)of all lesions. Risk factors for death were determined by multivariate regression analysis, andtime dependent receiver operating characteristic curves were used to determine the optimalWBTLG threshold predictive of death.Results The34patients had a total of120lesions confirmed by long-term clinical follow-upor pathological findings, of which118(98.3.0%),96(80.0%) and98(81.7%) could bedelineated by the Thbgd20,Th40and Th2.5thresholds, respectively. Thbgd20delineatedsignificantly more lesions than Th40and Th2.5(P<0.001) while Th2.5did not statisticallydelineated more lesions then Th40did (P=0.717). The optimal WBTLG cutoffs predictingpatient prognoses for1,2year，3years above were33.96,13.42, and13.42, respectively.The area under the curve predicting survival for1，2，3years and above were0.87,0.89,0.96, and0.96，respectively. Multivariate regression analysis showed that WBTLG (relativerisk [RR]1.005;95%confidence interval [CI]1.003-1.007, P<0.001) and post-surgical Tstaging (RR2.295;95%CI1.049-5.020, P=0.037) were significant predictors of survival, whereas age, post-surgical N and M stages, and F-18-FDG PET/CT based T, N and M stagesand number of lesions were not.Conclusion Whole body metabolic tumor burden using the Thbgdthreshold is a promisinglong-term independent prognostic factor in the post-surgical evaluation of males withesophageal squamous cell carcinoma.