A pilot study for texture analysis of ¹⁸F-FDG and ¹⁸F-FLT-PET/CT to predict tumor recurrence of patients with colorectal cancer who received surgery

This retrospective study was done to examine whether the heterogeneity in primary tumor F-18-fluorodeoxyglucose (¹⁸F-FDG) and ¹⁸F-3'-fluoro-3'-deoxythymidine (¹⁸F-FLT) distribution can predict prognosis of patients with colorectal cancer who received surgery. The enrolled 32 patients with colorectal cancer underwent both ¹⁸F-FDG- and ¹⁸F-FLT-PET/CT studies before surgery. Clinicopathological factors, stage, SUVmax, SUVmean, metabolic tumor volume (SUV ≥ 2.5), total lesion glycolysis, total lesion proliferation and seven texture heterogeneity parameters (coefficient of variation, local parameters: entropy, homogeneity, and dissimilarity; and regional parameters: intensity variability [IV], size-zone variability [SZV], and zone percentage [ZP]) were obtained. Progression free survival (PFS) was calculated by the Kaplan-Meier method. Prognostic significance was assessed by Cox proportional hazards analysis. Eight patients had eventually come to progression, and 24 patients were alive without progression during clinical follow-up [mean follow-up PFS; 55.9 months (range, 1-72)]. High stage (p = 0.004), high ¹⁸F-FDG-IV (p = 0.015), high ¹⁸F-FDG-SZV (p = 0.013) and high ¹⁸F-FLT-entropy (p = 0.015) were significant in predicting poor 5-year PFS. Other parameters did not predict the disease outcome. At bivariate analysis, disease event hazards ratios for ¹⁸F-FDG-IV and ¹⁸F-FDG-SZV remained significant when adjusted for stage and ¹⁸F-FLT-entropy (¹⁸F-FDG-IV; p = 0.004 [adjusted for stage], 0.007 [adjusted for ¹⁸F-FLT-entropy]; ¹⁸F-FDG-SZV; p = 0.028 [adjusted for stage], 0.040 [adjusted for ¹⁸F-FLT-entropy]). ¹⁸F-FDG PET heterogeneity parameters, IV and SZV, have a potential to be strong prognostic factors to predict PFS of patients with surgically resected colorectal cancer and are more useful than ¹⁸F-FLT-PET/CT heterogeneity parameters. (orig.)