Ga-68-DOTA-DiPSMA PET/CT Imaging: Biodistribution, Dosimetry, and Preliminary Application in Prostate Cancer

Purpose: This prospective trial aimed to evaluate the safety, dosimetry, and biodistribution of a novel theranostic probe Ga-68-DOTA-DiPSMA. Also, we have performed the first preliminary application with Ga-68-DOTA-DiPSMA in prostate cancer (PCa) patients.Methods: Five healthy volunteers and ten PCa patients were injected with an intravenous bolus of Ga-68-DOTA-DiPSMA. They received serial whole-body PET scans from the time of injection up to 60 min post-injection, with a second PET/CT scanning at 120 min post-injection. In PCa patients, low-dose CT scan and whole-body PET were performed with 2 min per bed position in 40 min post-injection. Absorbed organ doses and effective doses were calculated using OLINDA/EXM. Normal organ uptake and tumor lesion uptake were measured. A lesion-by-lesion analysis was performed.Results: Ga-68-DOTA-DiPSMA administration was safe and well-tolerated. The kidneys received the highest absorbed dose (114.46 +/- 29.28 mu Sv/MBq), followed by the urinary bladder wall (100.82 +/- 46.22 mu Sv/MBq) in accordance with the expected Prostate-Specific Membrane Antigen (PSMA) renal excretion of the tracer. The mean effective dose was 19.46 +/- 1.73 mu Sv/MBq. The SUVmax of Ga-68-DOTA-DiPSMA PET/CT for PCa lesions, bone metastases, and lymph node metastases was 4.41 +/- 2.72, 2.95 +/- 1.11, and 3.26 +/- 1.20, respectively.Conclusion: Injection of Ga-68-DOTA-DiPSMA is safe and associated with low absorbed and effective doses. Ga-68-DOTA-DiPSMA shows favorable kinetics and imaging characteristics in patients who warrant further head-to-head comparison to validate Ga-68-DOTA-DiPSMA as an alternative for gallium-68-labeled PSMA clinical PET. Low nonspecific uptake in normal organs of Ga-68-DOTA-DiPSMA indicates potential radioligand therapy (RLT) application when labeled with Lu-177, Y-90, or Ac-225.