Clinical role of fludeoxyglucose (18F) positron emission tomography/computed tomography (18F-FDG PET/CT) in patients with pancreatic neuroendocrine tumors

Clinical predictive markers for the malignant potential of pancreatic neuroendocrine tumors (PNETs) are limited without histological investigation. We reported previously that a loss of the regular enhancement pattern in preoperative computed tomography (CT) was correlated with the malignant tumor phenotype. This study aimed to establish whether the metabolic aspect of the tumor evaluated by fludeoxyglucose (18F) positron emission tomography/computed tomography 18F-FDG PET/CT is associated with the tumor imaging characteristics and postoperative oncological outcome. Among 77 patients who underwent surgery with curative intent for a PNET at our institution between 2001 and 2017, 24 who received 18F-FDG PET/CT before surgery were enrolled in this study. The clinical importance of the standardized uptake value (SUVmax) was investigated with regard to tumor progression and prognosis after curative surgery. There were four (16%) patients with insulinoma. The mean tumor size was 17 mm and when the median value of the SUVmax (= 2.0) was measured as the cut-off value, the SUVmax ≥ 2.0 group (n = 12) was associated with large tumor size (p = 0.021), high tumor grade (p = 0.015), and irregular pattern on CT (p = 0.0055). The SUVmax was not correlated with age, gender, whether the tumor was functioning or non-functioning, or lymph node metastasis. The SUVmax ≥ 2.0 group had significantly poorer disease-free survival (median, 3.5 vs 16.2 months; p = 0.023) and poorer overall survival (median, 8.8 vs 16.2 months; p = 0.042). An SUVmax ≥ 2.0 on 18F-FDG PET/CT might be associated with higher malignant potential of PNETs.