Purpose: To date, the prognostic value of (18)F-FDG PET/CT for patients with pancreatic neuroendocrine tumors (PNETs) has not been well characterized. We investigated the prognostic value of volumetric parameters using (18)F-FDG PET/CT in this patient population.
Methods: We retrospectively reviewed 20 cases of pathologically proven PNET in patients who had undergone pre-therapeutic (18)F-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, 1.2-95.4) 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 MTV of the primary tumor as measured by (18)F-FDG PET/CT along with the AJCC stage may be a significant independent prognostic factor for overall survival.
Keywords: 18F-FDG PET/CT; Metabolic tumor volume; Pancreatic neuroendocrine tumor; Prognosis; Total lesion glycolysis.