Comparison of DCFPyL and MRI in Detecting Locally Recurrent Prostate Cancer

1564 Objectives: Determine the accuracy, advantages, and limitations of 18F-DCFPyL PET/CT, a PSMA targeted PET agent, compared to MRI in detecting local recurrence of prostate cancer. Methods: This is a prospective IRB-approved study including 39 patients with documented biochemical recurrence (average PSA of 4.6 ng/mL, range 0.2-22.4 ng/mL), with negative conventional anatomical imaging, who had positive findings concerning for local recurrence of prostate cancer on either multiparametric MRI (mpMRI) or on 18F-DCFPyL PET imaging. 18F-DCFPyL PET lesion detection was compared with mpMRI findings, and subsequently correlated with biopsy when available (n=15). Results: 37 patients had abnormal findings on MRI (findings suspicious for local recurrence), whereas 24 patients had abnormal findings on 18F-DCFPyL. Of the 15 patients who subsequently underwent biopsy of prostate bed lesions, all 15 were positive for prostatic adenocarcinoma. 13 of the 15 biopsy-positive lesions were detected on mpMRI, and 13 were detected on 18F-DCFPyL. Two patients with biopsy-confirmed locally recurrent disease had false negative MRI results, but were positive on 18F-DCFPyL. Of these, one had prostatectomy as the initial primary therapy, and one had combination of radiation and androgen deprivation therapy. There were no lesions detected by mpMRI outside of the prostate bed in either patient. Two patients with biopsy-confirmed disease had false negative 18F-DCFPyL results, but were positive on MRI. Both of these had a combination of surgery and radiation therapy for initial treatment. 18F-DCFPyL was able to identity lesions outside the prostate bed in a total of 19 patients, including both patients with false negative 18F-DCFPyL within the prostate bed. PSA levels were higher in false negative 18F-DCFPyL cases (average PSA 14.5 ng/mL vs 4.5 ng/mL for all patients, and 4.7 ng/mL for biopsy-positive patients). Conclusions: 18F-DCFPyL PET/CT imaging detected local recurrence of prostate cancer in 86.7 % (13/15) patients with biochemical recurrence and biopsy-confirmation of local recurrence. 18F-DCFPyL can provide information complimentary to MRI in cases of local recurrence by detecting lesions outside of the pelvic field of view. There were significantly more patients with suspicious prostate bed lesions detected by MRI compared to 18F-DCFPyL, but without biopsy results available.