18 F-DCFPyL-PET/CT Imaging in Patients with Biochemical Recurrence Prostate Cancer after Primary Local Therapy

Objective: To investigate the lesion detection rate of 18 F-DCFPyL-PET/CT, a prostate-specific membrane antigen (PSMA) targeted PET agent, in biochemical relapse prostate cancer patients after primary local therapy. Methods: This is a prospective institutional review board-approved study of 90 patients with documented biochemical recurrence (median PSA 2.5 ng/mL, range 0.21-35.5 ng/mL) with negative conventional imaging after primary local therapies, including radical prostatectomy (n=38), radiation (n=27) or combination (n=25). Patients on androgen deprivation therapy were excluded. Patients underwent whole-body 18 F-DCFPyL-PET/CT (299.9±15.5 MBq) at 2 h p.i. PSMA-PET lesion detection rate was correlated with PSA, PSA kinetics and original primary tumor grade. Results: Seventy patients (77.8%) showed a positive PSMA-PET scan, identifying a total of 287 lesions: 37 prostate bed foci, 208 lymph nodes, and 42 bone/organ distant sites; 11 patients had a negative scan and 9 patients showed indeterminate lesions, which were considered negative in this study. The detection rates were 47.6% (n=10/21), 50% (n=5/10), 88.9% (n=8/9), and 94% (n=47/50) for PSA >0.2 to <0.5, 0.5 to <1.0, 1 to <2.0, and ≥ 2.0 ng/mL, respectively. In post-surgical patients, PSA, PSAdt and PSAvel correlated with PET results but the same was not true for post-radiation patients. These parameters also correlated with the extent of disease on PET (intrapelvic vs. extrapelvic). There was no significant difference between the rate of positive scans in patients with higher grade vs lower grade primary tumors (Gleason score ≥ 4+3 vs <3+4). Tumor recurrence was histology confirmed in 40% (28/70) of patients. On a per-patient basis, positive predictive value was 93.3% (95% CI, 77.6-99.2%) by histopathologic validation, and 96.2% (95% CI, 86.3-99.7%) by the combination of histology and imaging/clinical follow-up. Conclusions: 18 F-DCFPyL-PET/CT imaging offers high detection rates in biochemically recurrent prostate cancer patients; and is positive in about 50% of patients with PSA <0.5 ng/mL, which could substantially impact clinical management. In post-surgical patients, 18 F-DCFPyL-PET/CT correlates with PSA, PSAdt and PSAvel suggesting it may have prognostic value. 18 F-DCFPyL-PET/CT is highly promising for localizing sites of recurrent prostate cancer. metastatic patients compared to conventional imaging ( 11,12 ). Most experience has been reported for 68 Ga-labeled probes, and growing experience with 18 F-labeled-PSMA tracers. The latter with the advantage of a longer half-life (110 min for 18 F vs. 68 min for 68 Ga), enabling centralized production in a cyclotron facility, and more favorable positron energies for imaging. 18 F-DCFPyL is a second-generation PSMA-PET agent with high affinity for PCa ( 13-15 ). Here, we report the results of a prospective study of 18 F-DCFPyL-PET/CT for detection and localization of recurrent disease in patients with BCR. Specifically, we aimed to investigate the tumor detection rate as a function of PSA and PSA kinetics. We hypothesized that patients with 18 F-DCFPyL-PET/CT-positive scans were associated with more aggressive PSA kinetics than patients with negative scans.