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.