Abstract
1506
Objectives Neuroendocrine tumors of the pancreas (pNET) can occur in 8-17% of patients with von Hippel-Lindau disease (vHLD) and can metastasize in 11-20% of these cases. MRI and CT have a very high resolution; however, their sensitivity and specificity in the detection of pNET amongst cystic lesions in the pancreas is questionable. Ga-68 DOTATOC PET/CT is an established imaging method for the staging and restaging of patients with neuroendocrine tumors. In this study we aimed to look at i) the frequency of somatostatin receptor positive pNET in patients with vHLD, ii) the added value of Ga-68 DOTATOC PET in conjunction with morphological imaging (CT, MRI), and c) the effects of Ga-68 DOTATOC PET on treatment and follow-up.
Methods Ga-68 DOTATOC PET/3-phase contrast-enhanced CT was performed according to the guidelines in all consecutive vHLD-patients between 01/2013-11/2015. All patients underwent additional MRI imaging of the abdomen, spine, and head. Chromogranin A (CgA) was determined at the time of the PET/CT examination. A lesion seen on Ga-68 DOTATOC PET in the pancreas was defined as positive if the uptake was visually higher than in the surrounding tissues. Lesions were quantified using maximum SUV.
Results Overall, 20 patients (M:F 8:12; 44,7±11,1 yrs) were examined. Genetically, vHLD was type 1 and type 2 in 12 and 8 patients, respectively. Ga-68 DOTATOC PET/CT detected pNET in 11/20 (55%; 8 type 1, 3 type 2) of the patients whereas morphological imaging (CT or MRI) detected 9/20 (45%) of pNETs. CgA was mildly elevated in only 2/11 patients with pNET. The mean SUVmax of the pancreatic lesions was 23.9±24.8 (range 5.0-65.6). Mean size of the lesions on CT and/or MRI was 13±8.3 mm (range 6-38 mm); 62% were larger than 10 mm. In addition, somatostatin receptor (SR) positive hemangioblastomas were detected in 3 patients (SUVmax 2.1-10.1). One patient presented with SR positive lymph node metastasis. Type 1 vHLD was found to harbor pNETs more frequently (66.7%) than type 2 (37.5%). Two out of 3 patients with pNET which were followed up with Ga-68 DOTATOC PET/CT showed progressive disease within two years. Both patients had initial lesions > 10 mm.
Conclusions Comparing our results to historical data, we found a significantly higher frequency of pNETs in vHLD based on Ga-68 DOTATOC PET. pNETS were more prevalent in type 1 vHLD (66.7%) than in type 2 (37.5%). CT or MRI alone failed to detect pNETs in 10% of the patients. CgA was not a reliable parameter for detection of pNET in our patient population. Because of the potential malignancy of pNET > 10 mm, Ga-68 DOTATOC PET/CT is recommended as a diagnostic tool in vHLD patients.