Correlation between 18F-fluorodeoxyglucose positron emission tomography and pathologic differentiation in pancreatic cancer

The histopathological grade of differentiation is one of the significant prognostic factors in pancreatic adenocarcinoma. Especially in the patients with unresectable pancreatic cancer, it is important to obtain the prognostic information non-invasively to avoid unnecessary invasive procedure. The aim of the study was to correlate F-18-fluorodeoxyglucose (FDG) uptake with pathologic grade of pancreatic cancer, furthermore, to evaluate prognostic value of standardized uptake value (SUV). FDG-PET scans of 102 patients with histologically proven pancreas adenocarcinoma were retrospectively reviewed. SUV of the primary tumor was calculated for quantification analysis. Pathological differentiation was graded into well-, moderately, and poorly differentiated groups. One-way analysis of variance is performed to test the correlation of the SUV and histopathologic grades. Patients were assigned into 3 categorical groups, using SUV cut-offs of 4 and 7, respectively. Survival functions of different histologic grade and assigned groups according to SUV were estimated by Kaplan-Meier estimator and compared by log-rank test. Multivariate analysis was performed using the Cox proportional hazard regression model. There was a significant correlation of SUVs and pathologic grades (F = 4.97, p < 0.01). The mean SUV of well-, moderately and poorly differentiated groups was 4.93, 6.47 and 7.29, respectively. Tumor size, AJCC stage and treatment method were significantly related to the degree of FDG uptakes. SUV also shows a significant correlation with survival (p < 0.01), with better prognosis in lower SUV group. In multivariate analysis, the treatment method was the most strongly independent predictor (p < 0.01), followed by age (p = 0.04) and tumor size (p = 0.06). In moderately differentiated group, higher SUV showed significantly worse survival (p = 0.02). SUV is related with histologic grade and might be competitive predictor for patients' survival. Specifically, the prognosis of the patients with moderately differentiated pancreas adenocarcinoma could be stratified according to SUV.