The value of PSMA-based 18F-DCFPyL PET/CT imaging in patients with biochemical recurrence prostate cancer after primary local therapy

653 Objectives: To investigate lesion detection rate of 18F-DCFPyL PET/CT, a PSMA targeted PET agent, in patients with biochemical relapse prostate cancer after primary local therapy. Methods: This is a prospective IRB-approved study including 78 patients with documented biochemical recurrence (average PSA of 3.7 ng/mL, range 0.23-23.9 ng/mL) after local therapy, either radical prostatectomy (n= 30), post-radiation therapy (n=25) or combination (n=23), with negative conventional anatomical imaging. Patients underwent whole-body 18F-DCFPyL-PET/CT at 2 h p.i (299.9±15.5 MBq), and multiparametric pelvic MRI (mpMRI), 2 weeks apart. PSMA-PET lesion detection rate was correlated with mpMRI findings, and pre-scan PSA levels. Results: Sixty patients (76.9%) showed a positive PSMA-PET scan, identifying a total of 248 lesions: 28 in the prostate bed, 186 lymph nodes, and 34 bone/organ distant sites; ten patients had a negative scan and eight patients showed indeterminate lesions, which were also considered as having a negative scan. The detection rates were 55% (n=11/20), 50% (n=4/8), 87.5% (n=7/8), and 90.4% (n=38/42) for PSA levels of >0.2 to 0.5 to 1.0, >1 to 2.0, and ≥ 2.0 ng/mL, respectively. 18F-DCFPyL-PET findings and mpMRI findings were concordant for 35 lesions (14.1%), while 18F-DCFPyL detected additional 213 lesions (85.8%), 40% of them located outside the mpMR field of view. Out of 60 patients with positive PSMA-PET scan, tumor recurrence was confirmed by either biopsy (n=29), or matched mpMRI (n=7); 2 patients had a negative biopsy (rib fibrous dysplasia); 15 patients had lesions not amenable for biopsy; 4 patients refused biopsy, and 3 patients are pending for clinical decision. Patient accrual is ongoing for this trial and more results will be available at the time of presentation. Conclusions: 18F-DCFPyL-PET imaging is helpful in identifying suspicious lesions in 76.9% of patients with biochemical recurrence prostate cancer; and more importantly, it reveals a high number of positive findings in the range of low PSA values (