68Ga-DOTA-DiPSMA PET/CT Imaging: Biodistribution, Dosimetry and First Comparison with 68Ga-PSMA-11 in Prostate Cancer
Abstract PurposeThis prospective trial aimed to evaluate the safety, dosimetry, biodistribution, and diagnostic efficacy of a novel theranostic probe 68Ga-DOTA-DiPSMA. Also, we have performed the first comparison with 68Ga-PSMA-11 in prostate cancer (PCa) patients.MethodsFive healthy volunteers and ten PCa patients with a previous clinical 68Ga-PSMA-11 PET/CT were injected with an intravenous bolus of 68Ga-DOTA-DiPSMA with a dose of 1.85MBq/kg. Healthy volunteers 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, whole-body PET was performed with 2 min per bed position in 40 min post-injection. In addition, 68Ga-PSMA-11 scanning was performed on PCa patients within 10 days under the same acquisition procedure. Absorbed organ doses and effective doses were calculated using OLINDA/EXM. Normal organ uptake and tumor lesion uptake (SUVmax) were measured. A lesion-by-lesion analysis was performed.Results68Ga-DOTA-DiPSMA administration was safe and well-tolerated. The kidneys received the highest absorbed dose (114.46 ± 29.28 uSv/MBq), followed by the urinary bladder wall (100.82 ± 46.22 uSv/MBq) in accordance with the expected PSMA renal excretion of the tracer. The mean effective dose was 19.46 ± 1.73 μSv/MBq. The SUVmax of 68Ga-PSMA-11 and 68Ga-DOTA-DiPSMA PET/CT for PCa lesions, bone metastases, and lymph node metastases were 11.2 ± 10.76 vs. 4.41 ± 2.72, 7.6 ± 1.58 vs. 2.95 ± 1.11 and 4.86 ± 1.94 vs. 3.26 ± 1.2, respectively.ConclusionInjection of 68Ga-DOTA-DiPSMA is safe and associated with low absorbed and effective doses. Compared to 68Ga-PSMA-11, 68Ga-DOTA-DiPSMA shows comparable pharmacokinetics and detection ability in PCa patients that warrant further head-to-head comparison. Low non-specific uptake in salivary glands and kidneys of 68Ga-DOTA-DiPSMA indicates potential radioligand therapy (RLT) application when labeled with 177Lu, 90Y, or 225Ac.