Abstract
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Objectives Aim of this study was to evaluate the utility of VMP derived from 18F-FDG PET/CT in predicting the overall survival of patients diagnosed with stage III / IV PGBC
Methods FDG PET studies of 31 patients diagnosed with Stage III/ IV PGBC were retrospectively analyzed. FDG PET/CT was acquired 45 min after the injection of 370 - 440 MBq of 18F FDG. PET images were analyzed for VMP including maximal standardized uptake value (SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) using PET VCAR software. Semi-automated isoactivity contour VOI’s were generated utilizing the gradient threshold segmentation algorithm around all the metabolically active pathological lesions to obtain MTV, SUVmean and TLG. Overall survival was estimated as duration from the PET/CT imaging to death of the patient. ROC curves and Cox Hazard Regression Model were used for statistical analysis.
Results Of the total 31 patients (24 Females, 7 Males; Age range 38-75 yrs; mean 54.61 yrs), 26 patients died of the disease on follow up (mean duration 6.2 months, range 1-16 months). Median duration of overall survival was 5 months among the non survivors. The median follow up of the 5 survivors was 10 months (range 10-16). MTV and TLG exhibited greater accuracy than SUVmax on ROC analysis (AUC 0.769, 0.762 and 0.638 respectively) for prediction of event.However, there was no significant statistical association between time to death and SUVmax. Kaplan Meier curves were drawn utilizing these cutoffs of 82 cm3 for MTV and 270 g/ml x cm3 for TLG (derived from the ROC AUC data).On univariate analysis,MTV and TLG had significant effect on overall survival with a negative regression coefficient of 2.33 and 1.99 respectively.
Conclusions In our study, MTV and TLG showed significant prognostic significance on overall survival of advanced stage disease of PGBC. Thus these VMP may have impact on decision for therapeutic intervention and role in stratifying patients for future randomized trials.