Preliminary Evaluation of 68Ga-P16-093, a PET Radiotracer Targeting Prostate-Specific Membrane Antigen in Prostate Cancer

Purpose: Prostate-specific membrane antigen (PSMA) is a promising molecular target for imaging of prostate adenocarcinoma.Ga-68-P16-093, a small molecule PSMA ligand, previously showed equivalent diagnostic performance compared to Ga-68-PSMA-11 PET/CT in a pilot study of prostate cancer patients with biochemical recurrence (BCR). We performed a pilot study for further characterization of Ga-68-P16-093 including comparison to conventional imaging. Procedures: Patients were enrolled into two cohorts. The biodistribution cohort included 8 treated prostate cancer patients without recurrence, who underwent 6 whole body PET/CT scans with urine sampling for dosimetry using OLINDA/EXM. The dynamic cohort included 15 patients with BCR and 2 patients with primary prostate cancer. Two patients with renal cell carcinoma were also enrolled for exploratory use. A dynamic PET/CT was followed by 2 whole body scans for imaging protocol optimization based on bootstrapped replicates.Ga-68-P16-093 PET/CT was compared for diagnostic performance against available F-18-fluciclovine PET/CT, Tc-99m-MDP scintigraphy, diagnostic CT, and MRI. Results: Ga-68-P16-093 deposited similar effective dose (0.024 mSv/MBq) and lower urinary bladder dose (0.064 mSv/MBq) compared to Ga-68-PSMA-11. The kidneys were the critical organ (0.290 mSv/MBq).While higher injected activities were preferable, lower injected activities at 74-111 MBq (2-3 mCi) yielded 80% retention in signal-to-noise ratio.The optimal injection-to-scan interval was 60 min, with acceptable delay up to 90 min. Ga-68-P16-093 PET/CT showed superior diagnostic performance over conventional imaging with overall patient-level lesion detection rate of 71%, leading to a change in management in 42% of the patients. Conclusions: Based on its favorable imaging characteristics and diagnostic performance in prostate cancer,Ga-68-P16-093 PET/CT merits further investigation in larger clinical studies.

Automated summary

In this pilot study, Ga-68-P16-093 showed superior diagnostic performance compared to conventional imaging methods for prostate cancer, leading to changes in patient management. Further investigation in larger clinical studies is warranted to explore its potential.