Prognostic Value Of Metabolic Variables Of [¹⁸F]FDG PET/CT In Surgically Resected Stage ? Lung Adenocarcinoma

Part 1Comparison of different automated lesion delineation methods for metabolic tumor volume of 18F-FDG PET/CT in patients with stage I lung adenocarcinomaPurpose To investigate the suitable segmentation method in small,low uptake and heterogeneous nodules of stage I lung adenocarcinoma.Methods 133 stage I lung adenocarcinoma patients with 18F-FDG PET/CT scans were enrolled in this retrospective study.All lesions were divided into different groups according to nodule density,nodule size and the maximum standard uptake value(SUVmax)level.Four different PET segmentation methods were preformed,including percentage threshold of SUVmax(T42%and T42%×RC),gradient based threshold(adaptive iterative algorithm,AT-AIA),and background related threshold(adaptive thresholding at 40%SUVmax,AT40%)approaches.The MTVs were evaluated and compared with CT volume(CTV).Percentage volume error(%VE)compared to CTV was calculated and the correlations between MTVs and CTV were analyzed.Results AT-AIA had the highest accuracy in large,high uptake and solid nodules(72.5%,72.4%and 65.6%,respectively).AT40%had the highest accuracy in small,low uptake and non-solid nodules(56.6%,56.1%and 62.6%,respectively).In part-solid nodules,the accuracy of AT-AIA(60.0%)and AT40%(56.7%)were higher than that of T42%and T42%×RC.The MTV of AT-AIA was in excellent correlation with the CTV in solid nodules(R=0.831,P<0.001)and in high uptake nodules(R=0.830,P<0.001).The MTV of AT40%was in good correlation with the CTV in non-solid nodules(R=0.686,P=0.003)and in part-solid nodules(R=0.731,P<0.001).Conclusions AT40%showed best performance in small,low uptake,non-solid and part-solid lesions.AT-AIA was suitable for large,high uptake and solid lesions.Part 2Prognostic Value of Metabolic Variables of 18F-FDG PET/CT in Surgically Resected Stage I Lung AdenocarcinomaPurpose The objective of this study was to assess the prognostic value of metabolic tumor burden measured by positron emission tomography/computed tomography(PET/CT)in patients with stage I lung adenocarcinoma.Methods We reviewed 127 consecutive patients with pathologically proven stage I lung adenocarcinoma who underwent pre-treatment 18F-FDG PET/CT scans in our hospital from 2005 June to 2012 June.The maximum,mean and peak standardized uptake value(SUVmax,SUVmean and SUVpeak),metabolic tumor volume(MTV),total lesion glycolysis(TLG)and computed tomography volume(CTV)were measured.The Kaplan-Meier and Cox proportional hazards model were used with age,gender,TNM stage,clinical stage,histological grade,nodule type,tumor size and metabolic parameters to predict progression-free survival(PFS).The cut-off point was determined through ROC curve.Results In univariate analysis,the histological grade,nodule type,diameter(cut-off value of 2.0cm),CTV(6.56cm3),SUVmax(3.25g/ml),SUVmean(1.58g/ml),SUVpeak(1.84g/ml),MTV(4.80cm3)and TLG(10.40)were significantly associated with PFS(all P value<0.05).Patients with poorly differentiated adenocarcinoma,solid nodule type,large size,high metabolic tumor burden were associated with poor prognosis.In multivariate analysis,only histological grade was independent prognostic factors for progression with a P value of 0.005(RR,0.355;95%CI,0.173-0.728).Among five PET/CT metabolic parameters,only MTV was independent prognostic factors for progression with a P value of 0.031(RR,1.118;95%CI,1.010-1.237).Conclusions Histological grade was an independent predictor for progression in patients with stage I lung adenocarcinoma.Among five PET/CT metabolic parameters,only MTV was an independent predictor for progression.