(18)F-FACBC can be considered an alternative tracer superior to (11)C-choline in the setting of 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 11 C-choline PET/ CT (trigger PSA), PSA velocity (PSAvel), and PSA doubling time (PSAdt) on 11 C-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 11 C-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: 11 C-choline PET/CT detected disease relapse in 74 of 190 patients (38.9%). The detection rate of 11 C-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 5 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 5 0.04 and P 5 0.03). The 11 C-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 11 C-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 5 0.002; P 5 0.04) and PSAdt was found to be an independent factor only in patients with trigger PSA less than 2 ng/mL (P 5 0.05) using multivariate analysis. Conclusion: The 11 C-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.

The aim of the study was to assess which factors may influence 11 C-choline PET/CT detection rate in a population of recurrent prostate cancer (PCa) patients listed for salvage radiation therapy (S-RT) in an early phase of biochemical relapse, to select which patients could obtain the most benefit by performing restaging 11 C-choline PET/CT before S-RT. Methods: The study comprised 605 patients, treated with radical prostatectomy (RP) with curative intent for PCa who showed rising PSA levels after primary therapy and listed for S-RT. Prostate-specific antigen (PSA) values were .0.2 ng/mL and ,2 ng/mL (mean, 1.05 ng/mL; median, 1.07 ng/mL; range, 0.2-2 ng/m; SD, ±0.59). All patients were classified as N0 after RP. Seventeen of 605 patients received adjuvant RT together with RP, whereas 148 of 605 patients received androgen-deprivation therapy (ADT) at the time of PET/CT. PSA, PSA kinetics, Gleason score, age, time to biochemical relapse, ADT, and initial tumor stage were statistically analyzed to assess which factor could influence PET/CT positivity and the detection of local versus distant relapse. Results: 11 C-choline PET/CT was positive in 28.4% of patients (172/605). Eighty-three of 605 patients were positive in the pelvis (group A), distant metastasis (group B) were detected in 72 of 605 patients, and local and distant sites of relapse were detected in 17 of 605 patients (group C). At multivariate analysis, PSA, PSA doubling time (PSAdt), and ongoing ADT were significant predictors for positive scan results, whereas PSA and PSAdt were significantly related to distant relapse detection (P , 0.05). At the receiver-operatingcharacteristic analysis, a PSA value of 1.05 ng/mL and PSAdt of 5.95 mo were determined to be the optimal cutoff values in the prediction of a positive 11 C-choline PET/CT scan, with an area under the curve (AUC) of 0.625 for PSA and 0.677 for PSAdt. Conclusion: 11 Ccholine PET/CT may be suggested before S-RT during the early phase of biochemical relapse, to select patients who may benefit from this aggressive treatment. Particularly, patients showing fast PSA kinetics or PSA increasing levels despite ongoing ADT should be studied with 11 C-choline PET/CT before S-RT, considering the higher probability to detect positive findings outside the pelvis.

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