Prospective Multi-Institutional Study of 18F-DCFPyL PSMA PET/CT for Restaging Radio-Recurrent Prostate Cancer After Primary External Beam Radiotherapy or Brachytherapy

Abstract

Purpose: Prostate cancer recurrence after definitive radiotherapy is typically detected by a rising prostate-specific antigen (PSA) level and may represent isolated local recurrence or regional or distant metastatic disease. Positron emission tomography (PET) radiotracers targeting prostate-specific membrane antigen (PSMA), including 18F-DCFPyL, have shown promise for restaging recurrent prostate cancer after prostatectomy but are less well characterized for radio-recurrent prostate cancer. Methods and materials: This prospective, multi-institutional study evaluated the effect of adding 18F-DCFPyL PET/computed tomography (CT) to diagnostic imaging (DI; CT abdomen and pelvis, bone scan, and multiparametric magnetic resonance imaging of the pelvis) in men with radio-recurrent prostate cancer. All men underwent DI followed by 18F-DCFPyL PSMA PET/CT with local and central image interpretation; tie-break reads were performed when required. Management questionnaires were completed after DI and again after 18F-DCFPyL PET/CT. Discordance in disease patterns detected by 18F-DCFPyL PET/CT versus DI and changes in proposed management were characterized. Results: Seventy-nine men completed the study. Most men had T1 disease (62%) and Gleason score <7 (95%). Median PSA was 7.4 ng/mL at diagnosis and 4.8 ng/mL at relapse. DI detected isolated intraprostatic recurrence in 38 of 79 men (48%), regional nodal recurrence in 9 of 79 (11%), distant disease in 12 of 79 (15%), and no disease in 26 of 79 (33%). 18F-DCFPyL PET/CT detected isolated intraprostatic recurrence in 38 of 79 men (48%), regional nodal recurrence in 21 of 79 (27%), distant metastatic disease in 24 of 79 (30%), and no disease in 10 of 79 (13%). DI identified oligometastatic disease in 8 of 79 patients (10%), compared with 21 of 79 (27%) using 18F-DCFPyL PET/CT. 18F-DCFPyL PET/CT changed proposed management in 34 of 79 patients (43%). Conclusions: In men with radio-recurrent prostate cancer after primary radiotherapy, 18F-DCFPyL PSMA PET/CT identified extraprostatic disease in twice as many patients as DI and detected a recurrence site in 87% of men, compared with 67% using DI. 18F-DCFPyL PET/CT also identified potentially actionable disease, defined as prostate-only recurrence or oligometastatic disease, in 75% of men and changed proposed management in 43% of men.