Background Pancreatic neuroendocrine tumors (PNETs) present various histologic stages, and their clinical behavior ranges from benign to highly aggressive. World Health Organization (WHO) grading categorizes PNETs into 3 groups (G1, G2, and G3) based on proliferative activity. The aim of this study was to assess the clinical utility of 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) in preoperative differential diagnosis for various histologic grades of PNETs and in predicting postoperative prognosis in PNET patients. Methods We investigated prospectively 36 patients who underwent preoperative FDG-PET, received surgery for PNETs, and had resected specimens examined via histology. The maximum standardized uptake value (SUVmax) was determined on FDG-PET, and differentiating power between G1/G2 and G3 PNETs was examined using various SUVmax cutoff levels. We also evaluated the prognostic impact of FDG-PET findings using postoperative survival data. Results SUVmax significantly correlated with WHO grade (Spearman rank correlation 0.584; P =.0018), and the SUVmax of G3 tumors (5.0 ± 2.5; n = 4) was significantly higher than that of G1/G2 tumors (2.7 ± 1.6; n = 32; P =.0159). Using 2.5 as a cutoff SUVmax, the sensitivity, specificity, and accuracy of differentiating G3 tumors from G1/G2 tumors were 100.0%, 62.5%, and 66.7%, respectively. Furthermore, the SUVmax of FDG-PET (<2.5 vs ≥2.5) was significantly related to postoperative disease-free survival (P =.0463). Conclusion These results suggest that FDG-PET may be useful for differentiating G3 PNETs from G1/G2 PNETs and for predicting postoperative prognosis in PNET patients. This preliminary finding is expected to be confirmed by prospective validation with more patients.
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