Role of PSA kinetics in the detection rate of 18F-Choline PET/CT in restaging prostate cancer patients

Objectives To evaluate the role of PSA kinetics (velocity and doubling time) in the detection rate of 18F-Choline PET/CT (18FCH-PET/CT) in restaging prostate cancer patients.

Methods We retrospectively evaluated data of 52 patients (mean age 69.7 years, range 57-87), with PSA kinetics data available, with biochemical relapse after radical prostatectomy, who performed 18FCH-PET/CT. Age, Gleason score, trigger PSA, PSA velocity (PSAvel) and PSA doubling time (PSAdt) were evaluated by univariate logistic regression analysis in order to identify significant predictors related to a positive 18FCH-PET/CT. Moreover trigger PSA, PSA doubling time and PSA velocity were evaluated separately for positive and negative scans through the Mann-Whitney non-parametric test. Each 18FCH-PET/CT consisted on a five-min static acquisition of the pelvic region just after the radiopharmaceutical injection and a whole body scan at one hour post injection.

Results Positive detection rate of 18FCH-PET/CT was 52% (27/52 patients). Statistical analysis showed a significant correlation with age, trigger PSA level (mean 4.2 ng/ml, range 0.04-57.6 ng/ml), PSA doubling time (mean 9.3 months, range 0.9-76.5) and PSA velocity (7.0 ng/ml/years, range 0.1-55.8), considered separately (univariate analysis) with p-values < 0.05. PET positive patients (n: 27) presented fast PSA kinetics (mean PSAdt of 6.4 months and mean PSAvel of 10.7 ng/ml/year), while PET negative patients (n: 25) presented slow PSA kinetics (mean PSAdt of 13.9 months and mean PSAvel of 1.6 ng/ml/year). Differences were statistically significant p<0.05 (Mann-Whitney test).

Conclusions The detection rate increased with the increasing of trigger PSA, particularly in those patients who presented fast PSA kinetics (both doubling time and velocity). The observation of fast PSA kinetics can be considered as the optimal timing to perform 18FC-PET/CT.