e17536 Background: 68Ga-RM2 is a synthetic bombesin receptor antagonist targeting gastrin-releasing peptide receptors (GRPr) that are overexpressed in several human tumors, including prostate cancer (PC). Methods: We enrolled 114 men with BCR PC, 45-83-year-old (mean±SD: 68.2±7.0). Imaging started at 40-89 minutes (mean±SD: 51.3±9.2 after injection of 113.8-152.6 MBq (mean±SD: 140.7±6.4) of 68Ga-RM2 using a time-of-flight (TOF)-enabled simultaneous positron emission tomography (PET) / magnetic resonance imaging (MRI) scanner. Twenty-four and 23 patients also underwent 68Ga-PSMA11 and 18F-DCFPyL PET/CT, respectively. Results: All patients had rising PSA and negative conventional imaging prior to enrollment. 68Ga-RM2 PET identified recurrent PC in 78 of the 114 participants, while the simultaneous MRI was positive for PC in 45 of the 103 patients. Positivity rate of 68Ga-RM2 PET was: 31.8% for PSA < 0.5 ng/dl ( n= 22), 60% for PSA 0.5 – 1.0 ng/dl ( n= 15), 64.7% for PSA 1.0 – 2.0 ng/dl ( n= 17), 81.8% for PSA 2.0 – 5.0 ng/dl ( n= 22) and 87.2% for PSA > 5.0 ng/dl ( n= 38). PSA velocity values were 1.9±2.7 ng/ml/year (range: 0-9.1) in patients with negative PET scans and 5.8±9 ng/ml/year (range: 0.2-45.4) in patients with positive PET scans ( P: 0.01). Twenty-eight and 34 lesions were detected by 68Ga-RM2 PET and 68Ga-PSMA11 PET, respectively, while 25 lesions in 13 patients were identified by both radio-pharmaceuticals. The mean SUVmax ranged 1.6-51.2 (mean±SD:14.7±12.5) for PSMA and ranged 2.5-52.5 (mean±SD: 10.7±11.6) for RM2 ( P= 0.096). Three lesions in 2 patients were RM2-avid only (all lymph nodes) and 9 lesions in 7 patients were PSMA avid only (7 lymph nodes, 1 skeletal and 1 lung nodule). 32 and 48 lesions were detected by 68Ga-RM2 PET and 18F-DCFPyL PET, respectively. 28 lesions in 12 patients were identified by both radio-pharmaceuticals. The mean SUVmax ranged 1.7-79.3 (mean±SD: 22.2±23) for DCFPyL and ranged 1.7-46.8 (mean±SD: 7±9.2) for RM2 (P < 0.01). Four lesions in 2 patients were RM2 avid only (1 adrenal and 3 skeletal); 17 lesions in 6 patients were DCFPyL avid only (7 lymph nodes, 9 skeletal and 1 prostate). Conclusions: 68Ga-RM2 may identify higher risk patients given the highly statistically significant difference PSA velocity values between patients with negative and positive scans and may be a complementary radiopharmaceutical to the PSMA-targeting tracers to ultimately allow for personalized medicine. Clinical trial information: NCT02624518 .