Influence of Trigger PSA and PSA Kinetics on 11C-Choline PET/CT Detection Rate in Patients with Biochemical Relapse After Radical Prostatectomy

The purpose of this study was to investigate the effect of total prostate-specific antigen (PSA) at the time of C-11-choline PET/CT (trigger PSA), PSA velocity (PSAvel), and PSA doubling time (PSAdt) on C-11-choline PET/CT detection rate in patients treated with radical prostatectomy for prostate cancer, who showed biochemical failure during follow-up. Methods: A total of 190 patients treated with radical prostatectomy for prostate cancer who showed an increase in PSA (mean, 4.2; median, 2.1; range, 0.2-25.4 ng/mL) were retrospectively enrolled. All patients were studied with C-11-choline PET/CT. Patients were grouped according to trigger PSA (PSA <= 1 ng/mL, 1, PSA <= 2 ng/mL, 2, PSA <= 5 ng/mL, and PSA. 5 ng/mL). In 106 patients, data were available for calculation of PSAvel and PSAdt. Logistic regression analysis was used to determine whether there was a relationship between PSA levels and PSA kinetics and the rate of detection of relapse using PET. Results: C-11-choline PET/CT detected disease relapse in 74 of 190 patients (38.9%). The detection rate of 11C-choline PET/CT was 19%, 25%, 41%, and 67% in the 4 subgroups-PSA <= 1 ng/mL (51 patients), 1, PSA <= 2 ng/mL (39 patients), 2, PSA <= 5 ng/mL (51 patients), and PSA. 5 ng/mL (49 patients)-respectively. Trigger PSA values were statistically different between PET-positive patients (median PSA, 4.0 ng/mL) and PET-negative patients (median PSA, 1.4 ng/mL) (P = 0.0001). Receiver-operating-characteristic analysis showed an optimal cutoff point for trigger PSA of 2.43 ng/mL (area under the curve, 0.76). In 106 patients, PSAdt and PSAvel values were statistically different between patients with PET-positive and-negative scan findings (P = 0.04 and P = 0.03). The C-11-choline PET/CT detection rate was 12%, 34%, 42%, and 70%, respectively, in patients with PSAvel, 1 ng/mL/y (33 patients), 1, PSAvel <= 2 ng/mL/y (26 patients), 2, PSAvel <= 5 ng/mL/y (19 patients), and PSAvel. 5 ng/mL/y (28 patients). The C-11-choline PET/CT detection rate was 20%, 40%, 48%, and 60%, respectively, in patients with PSAdt. 6 mo (45 patients), 4, PSAdt <= 6 mo (20 patients), 2, PSAdt <= 4 mo (31 patients), and PSAdt <= 2 mo (10 patients). There was no statistical difference between PET-positive and-negative scan detection rates according to the Gleason score, pT and N status, patient age, or duration between surgery and biochemical relapse. Trigger PSA and PSAvel were found to be independent predictive factors for a PET-positive result (P = 0.002; P = 0.04) and PSAdt was found to be an independent factor only in patients with trigger PSA less than 2 ng/mL (P = 0.05) using multivariate analysis. Conclusion: The C-11-choline PET/CT detection rate is influenced by trigger PSA, PSAdt, and PSAvel. This finding could be used to improve the selection of patients for scanning by reducing the number of false-negative scans and increasing the detection rate of disease in patients with early relapse and potentially curative disease.