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

Abstract

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.

Fig. 1

Kaplan-Meier survival curves according to the MTV of the primary tumor (a) and stage (b) in patients with pancreatic neuroendocrine tumors. Both higher MTV and higher stage were significantly associated with worse prognoses

Fig. 2

Representative ¹⁸F-FDG PET and PET/CT fusion images in high-MTV (a) and low-MTV (b) pancreatic neuroendocrine tumors (PNETs). a PET/CT of a 60-year-old male patient with a PNET that showed a high MTV (98.9 cm³) of the primary tumor, with a poor overall prognosis (overall survival = 13.6 months). b PET/CT of a 59-year-old male patient with a PNET that showed a low MTV (13.6 cm³) of the primary tumor, with a good overall prognosis (overall survival = 68.9 months)