PSMA- and GRPR-Targeted PET: Results from 50 Patients with Biochemically Recurrent Prostate Cancer

Novel radiopharmaceuticals for PET are being evaluated for the diagnosis of biochemical recurrence (BCR) of prostate cancer (PC). We compared the gastrin-releasing peptide receptor-targeting Ga-68-RM2 with the prostate-specific membrane antigen (PSMA)-targeting Ga-68-PSMA11 and F-18-DCFPyL. Methods: Fifty patients underwent both Ga-68-RM2 PET/MRI and Ga-68-PSMA11 (n = 23) or 18F-DCFPyL (n = 27) PET/CT at an interval ranging from 1 to 60 d (mean +/- SD, 15.8 +/- 17.7 d). SUVmax was collected for all lesions. Results: Ga-68-RM2 PET was positive in 35 and negative in 15 of the 50 patients. Ga-68-PSMA11/F-18-DCFPyL PET was positive in 37 and negative in 13 of the 50 patients. Both scans detected 70 lesions in 32 patients. Forty-three lesions in 18 patients were identified on only 1 scan: Ga-68-RM2 detected 7 more lesions in 4 patients, whereas Ga-68-PSMA11/(FDCFPyL)-F-18 detected 36 more lesions in 13 patients. Conclusion: Ga-68-RM2 remains a valuable radiopharmaceutical even when compared with the more widely used Ga-68-PSMA11/F-18-DCFPyL in the evaluation of BCR of PC. Larger studies are needed to verify that identifying patients for whom these 2 classes of radiopharmaceuticals are complementary may ultimately allow for personalized medicine.

Automated summary

The novel radiopharmaceutical Ga-68-RM2 shows promising results in the diagnosis of biochemical recurrence of prostate cancer compared to Ga-68-PSMA11 and F-18-DCFPyL. Larger studies are needed to determine the complementary use of these radiopharmaceuticals for personalized medicine.