Preliminary clinical experience of cholecystokinin-2 receptor PET/CT imaging using the 68 Ga-labeled minigastrin analog DOTA-MGS5 in patients with medullary thyroid cancer.

PET/CT imaging was performed in patients with advanced medullary thyroid cancer (MTC) with the new 68 Ga-labeled minigastrin analog DOTA-DGlu-Ala-Tyr-Gly-Trp-(N-Me)Nle-Asp-1-Nal-NH2 (68 Ga-DOTA-MGS5) to evaluate the cholecystokinin-2 receptor expression status. Methods: Six patients with advanced MTC underwent PET/CT imaging with 68 Ga-DOTA-MGS5. From the images acquired one and two hours post injection (p.i.) preliminary data on the biodistribution and tumor targeting properties were evaluated in a retrospective analysis. Results: A total of 87 lesions with increased radiotracer uptake considered malignant (two local recurrence, eight lymph nodes, 27 liver and 50 bone lesions) was detected. In general, radiotracer accumulation in lesions was found higher two hours as compared to one hour p.i. (mean SUVmax /SUVmean of 7.2/4.4 versus 6.0/3.6). Conclusion: The preliminary results clearly demonstrate the potential of 68 Ga-DOTA-MGS5 PET/CT in detecting local recurrence and metastases in patients with advanced MTC.