Prospective head-to-head comparison of 18F-fluciclovine and 68Ga-PSMA-11 PET/CT for localization of prostate cancer biochemical recurrence after primary prostatectomy.

Abstract

15 Background: 18F-Fluciclovine PET/CT (FACBC) is standard-of-care in US for localization of prostate cancer (PCa) biochemical recurrence (BCR) after definitive therapy. 68Ga-PSMA-11 PET/CT (PSMA) detects PCa BCR even at low prostate-specific antigen (PSA) levels (<2.0 ng/mL). We conducted a single-center prospective head-to-head comparison of these 2 PET/CT imaging tracers for localizing PCa BCR after radical prostatectomy (RP) in patients with PSA < 2.0 ng/ml. Methods: Patients with PCa BCR after RP and PSA levels ranging from ≥0.2 to ≤2.0 ng/mL without any prior salvage therapy were eligible. All patients underwent FACBC and PSMA scans within ≤15 days. Images analysis was performed a) by on-site clinical reading and b) by 3 blinded international expert readers for each modality. Detection rates on per-patient and per-region based analysis served as primary study endpoints. Based on literature data we hypothesized a detection rate difference of 22% in favor of PSMA. A power analysis determined a sample size of 50 patients. Results: The 50 patients were enrolled from March to September 2018. Median PSA level was 0.50 ng/ml. Median time interval between the 2 scans was 6 days. We present here the preliminary results from the non-blinded clinical reads. Detection rate on a per-patient basis was 69% for PSMA and 34% for FACBC. Concordant findings were observed in 30/49 patients (61%): 16/49 (32%) with both positive scans and 14/49 (29%) with both negative scans. Discordant findings were observed in 19/49 patients (39%): 18/49 (37%) had a positive PSMA but a negative FACBC scan while 1/49 (2%) had a positive FACBC with a negative PSMA (local recurrence). Detection rates were consistently lower for FACBC than for PSMA for all regions: Prostate bed (12% vs 20%), pelvic nodes (14% vs 37%), extra-pelvic nodes (2% vs 8%), skeleton (2% vs 8%) and visceral organs (2% vs 6%). Conclusions: This preliminary analysis from the non-blinded on-site clinical reads demonstrates prospectively that PSMA detection rates is more than double the FACBC detection rate in patients with PCa BCR after RP and with PSA ≤2.0 ng/ml. Clinical trial information: NCT03515577.