Heterogeneity index evaluated by slope of linear regression on 18F-FDG PET/CT as a prognostic marker for predicting tumor recurrence in pancreatic ductal adenocarcinoma.

Abstract

18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) has been investigated as a method to predict pancreatic cancer recurrence after pancreatic surgery. We evaluated the recently introduced heterogeneity indices of 18F-FDG PET/CT used for predicting pancreatic cancer recurrence after surgery and compared them with current clinicopathologic and 18F-FDG PET/CT parameters. A total of 93 pancreatic ductal adenocarcinoma patients (M:F=60:33, mean age=64.2±9.1years) who underwent preoperative 18F-FDG PET/CT following pancreatic surgery were retrospectively enrolled. The standardized uptake values (SUVs) and tumor-to-background ratios (TBR) were measured on each 18F-FDG PET/CT, as metabolic parameters. Metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were examined as volumetric parameters. The coefficient of variance (heterogeneity index-1; SUVmean divided by the standard deviation) and linear regression slopes (heterogeneity index-2) of the MTV, according to SUV thresholds of 2.0, 2.5 and 3.0, were evaluated as heterogeneity indices. Predictive values of clinicopathologic and 18F-FDG PET/CT parameters and heterogeneity indices were compared in terms of pancreatic cancer recurrence. Seventy patients (75.3%) showed recurrence after pancreatic cancer surgery (mean recurrence=9.4±8.4months). Comparing the recurrence and no recurrence patients, all of the 18F-FDG PET/CT parameters and heterogeneity indices demonstrated significant differences. In univariate Cox-regression analyses, MTV (P=0.013), TLG (P=0.007), and heterogeneity index-2 (P=0.027) were significant. Among the clinicopathologic parameters, CA19-9 (P=0.025) and venous invasion (P=0.002) were selected as significant parameters. In multivariate Cox-regression analyses, MTV (P=0.005), TLG (P=0.004), and heterogeneity index-2 (P=0.016) with venous invasion (P<0.001, 0.001, and 0.001, respectively) demonstrated significant results. The heterogeneity index obtained using the linear regression slope, could be an effective predictor of pancreatic cancer recurrence after pancreatic cancer surgery, in addition to 18F-FDG PET/CT volumetric parameters and clinicopathologic parameters.