Dynamic (68)Ga-DOTA(0)-Tyr(3)-octreotate positron emission tomography-computed tomography for the evaluation of pancreatic neuroendocrine tumors: a pilot study

BACKGROUND: (68)Ga-DOTA(0)-Tyr(3)-octreotate ((68)Ga-DOTATATE) is a radiolabeled somatostatin analog used for the diagnosis of pancreatic neuroendocrine tumors (pNETs), and standardized uptake value (SUV) measurements for therapeutic monitoring is recommended. However, changes in net influx rate (K(i)) may better reflect treatment effects than may those of the SUV. The aim of this study was to investigate the value of dynamic (68)Ga-DOTATATE positron emission tomography-computed tomography (PET-CT) in the evaluation of pNETs. METHODS: Dynamic PET-CT scans over 60 min were acquired for 7 patients with localized pancreatic mass before surgery. Maximal and mean SUV (SUV(max) and SUV(mean)) were measured in tumors and normal pancreatic body as reference tissue (RT). Time-activity curves (TACs) were extracted from tumors and RT. A 2-tissue compartment model was used to calculate the rate constants K(1), k(2), and k(3) (min(−1)); K(i) (mL/g/min); and K(1):k(2) ratio. The following statistical tests were used to evaluate the results: the Shapiro-Wilk, Student t test, Mann-Whitney, Spearman, and Pearson rank correlation tests. RESULTS: Among 6 patients, 8 primary tumors were histopathologically proven to be pNETs. Moreover, 6 lesions with high uptake of (68)Ga-DOTATATE showed an ascending TAC pattern, while 2 lesions with no or low uptake showed a descending TAC pattern. The mean SUV(max) and SUV(mean) of pNETs were 46.4±40.2 (range, 3.9–109.9) and 21.9±16.0 (range, 0.5–42.8), respectively, which were significantly higher than the SUV(max) of 4.2±0.6 (range, 3.1–4.9) and the SUV(mean) of 2.7±1.0 (range, 1.4–3.6) for the RT (P=0.021 and P=0.036), respectively. The K(i) of pNETs was statistically higher than that of the RT [pNET: 0.366±0.372 (range, 0.019–0.992); RT: 0.060±0.017 (range, 0.04–0.08); P=0.036]. The mean K(1):k(2) ratio in pNETs was 12-fold higher than that of RT (6.06 vs. 0.50). In pNETs, there was a positive correlation between SUV(max) and K(i) (r=0.952; P<0.001) and between SUV(mean) and K(i) (r=0.905; P=0.002). Another patient was diagnosed with intrapancreatic accessory spleen. CONCLUSIONS: The uptake of (68)Ga-DOTATATE by pNETs can be explained by its high K(i) value and K(1):k(2) ratio. Dynamic (68)Ga-DOTATATE PET-CT can serve as a potential tool for evaluating pNETs and support the further assessment of a larger cohort of patients.