Effect of hormonal therapy on 18F-fluciclovine PET/CT in the detection of prostate cancer recurrence, localization of metastatic disease, and correlation with prostate-specific antigen.

INTRODUCTION: 18F-Fluciclovine, is a positron emission tomography (PET) radiotracer approved for the localization of sites of prostate cancer recurrence in men with a rising prostate-specific antigen (PSA) after definitive treatment. To explore the impact of androgen deprivation therapy (ADT) on the performance of 18F-fluciclovine, we conducted a retrospective analysis to compare the 18F-fluciclovine PET/CT positivity rate in patients receiving ADT at the time of the scan with the rate achieved in patients not receiving ADT. METHODS: A retrospective review of data from patients who underwent 18F-fluciclovine PET/CT for biochemical recurrence of prostate cancer between December 2016 to March 2020 was performed. The cohort was divided into an ADT group (patient reportedly on ADT) and a non-ADT group (not currently receiving ADT). Patients with unknown ADT status or undetectable/unknown PSA were excluded. For each group, the number of positive 18F-fluciclovine PET/CT scans (positivity rate) was evaluated for the whole body, prostate/bed, and extraprostatic regions and rates were correlated with PSA. The Fisher's Exact test was applied to establish the significance between the ADT and non-ADT positivity groups. Mantel-Haenszel trend test was performed to assess linearity between the positivity rate and PSA level. RESULTS: In 320 patients, the status of ADT was known. At the time of the 18F-fluciclovine scan, 68/320 (21%) patients were on ADT, while 252/320 (79%) were not. The median Gleason score was 8 (range of 6-10) in the ADT group vs. 7 (range of 6-10) in the non-ADT group (P < 0.001). Overall, positivity rates demonstrated no statistical significance between the ADT and non-ADT groups; Positivity rates (ADT vs. non-ADT) were 82% (56/68) vs. 82% (206/252) for the whole body, 57% (39/68) vs. 60% (152/252) for prostate/bed, and 60% (41/68) vs. 53% (133/252) for extraprostatic regions (P > 0.05). A positive linear correlation was noted between PSA and each group's positivity rate (P < 0.01). However, no significant difference was observed between ADT and non-ADT groups at different PSA levels (P > 0.05). CONCLUSIONS: Detection of prostate cancer recurrence with 18F-fluciclovine PET/CT is not significantly influenced by ADT, suggesting that localization of disease in patients with detectable PSA who are receiving ADT is feasible with 18F-fluciclovine.

Positivity Rate of [18F]Fluciclovine PET/CT in Patients with Suspected Prostate Cancer Recurrence at PSA Levels Below 1 ng/mL.

PURPOSE: Early and precise localization of recurrent prostate cancer lesions after local therapy facilitates optimal disease management. Here, we present results from a single-center study to evaluate the utility of [18F]fluciclovine PET/CT to localize prostate cancer recurrence in patients with PSA <1 ng/mL. PROCEDURES: Data from men who underwent [18F]fluciclovine PET/CT (August 2016-March 2020) for suspected recurrent prostate cancer and who had a PSA value <1ng/mL were retrospectively reviewed. The number of positive scans (positivity rates, PR) was calculated for the whole body, prostate/bed, and extraprostatic regions (pelvic or extrapelvic lymph nodes, bones, and soft tissue). PR were stratified by pre-scan PSA. RESULTS: Data from 113 patients were included. In total, 98 (87%) were post-prostatectomy and 15 (13%) had received non-surgical primary therapy. Twenty patients (18%) were receiving ADT at the time of the scan, 91 (81%) were not, and ADT status was not known for 2 (1.8%) patients. The overall PR at PSA <1ng/mL was 59% (67/113). For the prostate/bed, it was 35% (40/113), and for extraprostatic locations, it was 37% (42/113). At PSA >0-<0.2, 0.2-<0.5, and 0.5-<1 ng/mL, the overall PR was 43% (10/23), 70% (35/50), and 55% (22/40), respectively. In the prostate/bed, these were 13% (3/23), 50% (25/50), and 30% (12/40), respectively, and in extraprostatic lesions were 30% (7/23), 44% (22/50), and 33% (13/40), respectively. Pelvic lymph nodes were the most common site for extraprostatic lesions (29/113, 26%). PR in extrapelvic lymph nodes, bone, and soft tissue were 8.0%, 12%, and 3.5%, respectively. Soft tissue lesions comprised lung nodules (n=3) and a perirectal mass implant (n=1). CONCLUSIONS: Despite low PSA values, more than half of patients had positive [18F]fluciclovine PET/CT findings. Patients with low PSA levels may demonstrate suspicious findings outside of the pelvis, including abdominal lymph nodes and metastatic disease to bones and lungs.