Preliminary Clinical Experience with Cholecystokinin-2 Receptor PET/CT Using the Ga-Labeled Minigastrin Analog DOTA-MGS5 in Patients with Medullary Thyroid Cancer.

PET/CT with the new Ga-labeled minigastrin analog DOTA-dGlu-Ala-Tyr-Gly-Trp-(-Me)Nle-Asp-1-Nal-NH (Ga-DOTA-MGS5) was performed on patients with advanced medullary thyroid cancer (MTC) to evaluate cholecystokinin-2 receptor expression status. Six patients with advanced MTC underwent PET/CT with Ga-DOTA-MGS5. From the images acquired 1 and 2 h after injection, preliminary data on the biodistribution and tumor-targeting properties were evaluated in a retrospective analysis. In total, 87 lesions with increased radiotracer uptake considered malignant were detected (2 local recurrences, 8 lymph node lesions, 27 liver lesions, and 50 bone lesions). In general, radiotracer accumulation in lesions was higher at 2 h than at 1 h after injection (mean SUV, 7.2 vs. 6.0, respectively; mean SUV, 4.4 vs. 3.6, respectively). The preliminary results clearly demonstrate the potential of Ga-DOTA-MGS5 PET/CT in detecting local recurrence and metastases in patients with advanced MTC.