Diagnostic performance of somatostatin receptor PET/CT using 68 Ga-DOTANOC in gastrinoma patients with negative or equivocal CT findings Niraj Naswa, Punit Sharma, Ramya Soundararajan, Sellam Karunanithi, Aftab Hasan Nazar, Rakesh Kumar, Arun Malhotra, Chandrasekhar Bal Department of Nuclear Medicine, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India Abstract Purpose: Contrast-enhanced CT (CECT) is a standard investigative procedure in the localization of gastrino- mas. Small tumors are often missed and metastatic lesions may remain occult on CT. The purpose of present study was to prospectively evaluate the diagnos- tic performance of 68 Ga-labeled [1,4,7,10-tetraazacyclo- dodecane-1,4,7,10-tetraacetic acid]-1-NaI 3 -Octreotide ( 68 Ga-DOTANOC) positron emission tomography/com- puted tomography (PET/CT) in gastrinoma patients with negative or equivocal CT findings. Methods: Twenty-five patients (age 46.6 ± 13.3 years; male 60%) with clinical/biochemical diagnosis of gas- trinoma and negative or equivocal findings on CECT were prospectively evaluated. All of them underwent 68 Ga-DOTANOC PET/CT which was evaluated by two nuclear medicine physicians in consensus. Combination of histopathology, serum gastrin, endoscopy, and follow- up imaging were taken as reference standard. Results: 68 Ga-DOTANOC PET/CT was positive in 17 patients and negative in 8 patients, yielding an overall detection rate of 68%. It was positive 13/20 patients who underwent baseline evaluation and in 4/5 post-treatment patients. Of the 11 patients who had a negative CT result, 68 Ga-DOTANOC PET/CT was positive in four cases (detection rate 36.4%), while it was abnormal in 13/14 patients who had equivocal CT findings (detection rate 92.8%). Diagnostic performance of 68 Ga-DOTANOC PET/CT was superior in patients with equivocal CECT findings than that in patients with negative CECT (P = 0.010). Conclusion: 68 Ga-DOTANOC PET/CT appears to be useful in patients with gastrinoma with negative or equivocal results on CECT, especially the latter group. Key words: Gastrinoma— 68 Ga-DOTANOC—PET/ CT—Contrast-enhanced CT Optimal management of patients with gastrinomas requires accurate tumor localization and staging. Various imaging methods have been evaluated including ultra- sonography, computed axial tomography (CT), magnetic resonance imaging (MRI), endoscopic ultrasonography (EUS), selective arteriography, transhepatic portal venous sampling, and secretin angiography [1–4]. No single method or combination of methods has emerged as a gold standard for identifying the location of the primary tumor(s) and predicting the presence and extent of metastases. Like many other neuroendocrine tumors (NETs), gastrinomas also express somatostatin receptors (SSTRs) [5]. This SSTR expression has been exploited for imaging of gastrinomas with radiolabeled somatostatin analogs [6]. Till recently, 111 In-DTPA-phenyl-octreotide was the most common agent used for somatostatin receptor scintigraphy (SRS) of gastrinomas. It was found to be the most sensitive imaging modality for the detec- tion of primary or metastatic gastrinomas [7]. However, 111 In-DTPA-phenyl- octreotide SRS suffers from the drawback of limited resolution of single photon emission tomography (SPECT) technology as well as unfavorable biodistribution in the liver and spleen, obscuring smaller lesions. Correspondence to: Chandrasekhar Bal; email: csbal@hotmail.com ª Springer Science+Business Media, LLC 2012 Abdominal Imaging Abdom Imaging (2012) DOI: 10.1007/s00261-012-9925-z