Clinical utility of 18F-Fluciclovine PET/CT in recurrent prostate cancer with very low (≤0.3 ng/mL) prostate-specific antigen levels.

The purpose of this study was to evaluate ¹⁸F-fluciclovine PET/CT detection rates in the evaluation of biochemical recurrence in prostate cancer patients with very low (≤0.3 ng/mL) serum prostate-specific antigen (PSA) levels following definitive treatment. Prostate cancer patients with biochemical recurrence and very low serum PSA (≤0.3 ng/mL) who underwent clinical ¹⁸F-fluciclovine PET/CT were included in this single-institution retrospective study. PET/CT clinical reports at the time of interpretation were reviewed and categorized as positive or negative. In patients who had further evaluation with imaging and/or biopsy, the results were recorded to determine the true detection rate. Of the 64 eligible patients with very low serum PSA (median serum PSA of 0.17 ng/mL), 57.8% (37/64) scans were categorized as positive. Stratified by PSA levels, positivity rates were 43.8% (7/16), 60.0% (15/25) and 65.2% (15/23) for PSA<0.1 ng/mL, 0.1-<0.2 ng/mL and 0.2-≤0.3 ng/mL, respectively. The most common location of disease was the prostate bed (73%), followed by pelvic lymph nodes (22%) and distant disease (14%). In the small subset of patients who had further evaluation after a positive study (n=7), all had confirmed disease with a positive predictive value of 100%. In conclusion, among prostate cancer patients with biochemical recurrence, ¹⁸F-fluciclovine PET/CT is useful in patients with very low serum PSA of ≤0.3 ng/mL, with a 57.8% positivity rate, higher than previously reported. Though standard of truth could only be ascertained in 19% (7/37) of patients with a positive study, the positive predictive value was 100%.