Prognostic Value of Volume-Based Metabolic Parameters Measured by 18F-FDG PET/CT of Pancreatic Neuroendocrine Tumors

Purpose To date, the prognostic value of F-18-FDG PET/CT for patients with pancreatic neuroendocrine tumors (PNETs) has not been well characterized. We investigated the prognostic value of volumetric parameters using 18F-FDG PET/CT in this patient population. Methods We retrospectively reviewed 20 cases of pathologically proven PNET in patients who had undergone pretherapeutic F-18-FDG PET/CT. PET parameters including maximum and average standardized uptake values (SUVmax, SUVave), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the primary tumor were measured using a threshold SUV to determine the boundaries of the tumors. Univariate and multivariate survival analyses were performed with adjustments for PET parameters and other clinical values. Results The median clinical follow-up was 22.3 (range, 1.295.4) months. Cancer-related death occurred in 5 of 20 patients (25 %). Patients had clinical or pathological stages of I in seven patients, II in six patients, III in three patient, and IV in four patients. According to the WHO histological classification of subtypes, 3 patients exhibited well-differentiated PNETs, 13 patients had well-differentiated endocrine carcinomas, and 4 had poorly differentiatedendocrine carcinomas. Univariate analysis showed that tumor size (p= 0.028), AJCC stage (p= 0.009), T stage (p= 0.028), M stage (p= 0.029), treatment modality (p= 0.045), MTV (p= 0.003) and TLG (p= 0.027) were significant predictors of overall survival. On multivariate analysis, MTV (HR= 10.859, p= 0.031) was a significant independent predictor of overall survival along with the AJCC stage (HR= 11.556, p= 0.027). Conclusion In patients with PNETs, the MTVof the primary tumor asmeasured by F-18-FDG PET/CTalong with the AJCC stage may be a significant independent prognostic factor for overall survival.