68Ga-DOTA-NOC PET/CT Imaging of Neuroendocrine Tumors: Comparison with 111In-DTPA-Octreotide (OctreoScan®)

Recent data have indicated that Ga-68-DOTA-NOC positron emission tomography/X-ray computed tomography (PET/CT) may yield improved images in a shorter acquisition protocol than In-111-DTPA-octreotide (OctreoScanA (R), OCT). Therefore, we performed a prospective comparison of Ga-68-DOTA-NOC and OCT for the detection of neuroendocrine tumors (NETs). Nineteen patients (eight carcinoid, nine pancreatic NETs, and two NE carcinoma of unknown origin) with previous positive OCT scans underwent Ga-68-DOTA-NOC PET/CT and OCT single-photon emission computed tomography imaging for staging or follow-up. Findings were compared by region and verified with conventional imaging. All images of both modalities demonstrated focal uptake, often at multiple sites. Ga-68-DOTA-NOC images were clearer than OCT images, facilitating interpretation. Similar foci were identified with both modalities in 41 regions, with additional foci on Ga-68-DOTA-NOC in 21 and on OCT in 15 regions. CT, magnetic resonance imaging, or ultrasound confirmed the concordant findings in 31 of 41 regions and findings seen with Ga-68-DOTA-NOC only in 15 of 21 regions. Findings seen with OCT only were less clear and were only confirmed in 4 of 15 regions. Ga-68-DOTA-NOC had impact on staging in four patients and on management in three patients. Although Ga-68-DOTA-NOC and OCT images were similar, in this study, Ga-68-DOTA-NOC demonstrated more true positive tumor foci and was better tolerated by patients. This direct comparison supports replacement of OCT with Ga-68-DOTA-NOC-PET/CT in the evaluation of NETs.