Is the detection rate of 18F-choline PET/CT influenced by androgen-deprivation therapy?

Purpose To evaluate if the detection rate (DR) of F-18-choline (18F-CH) PET/CT is influenced by androgen-deprivation therapy (ADT) in patients with prostate cancer (PC) already treated with radical intent and presenting biochemical relapse. Materials and methods We have retrospectively evaluated F-18-CH PET/CT scans of 325 consecutive PC patients enrolled in the period November 2009 to December 2012 previously treated with radical intent and referred to our centre to perform F-18-CH PET/CT for biochemical relapse. Two different groups of patients were evaluated. group A included the whole sample of 325 patients (mean age 70 years, range: 49-86) who presented trigger PSA between 0.1 and 80 ng/ml (mean 5.5 ng/ml), and group B included 187 patients (mean age 70 years, range 49-86) with medium-low levels of trigger PSA ranging between 0.5 and 5 ng/ml (mean PSA 2.1 ng/ml); group B was chosen in order to obtain a more homogeneous group of patients in terms of PSA values also excluding both very low and very high PSA levels avoiding the a priori higher probability of negative or positive PET scan, respectively. At the time of examination, 139 patients from group A and 72 patients from group B were under ADT: these patients were considered to be hormone-resistant PC patients because from their oncologic history (> 18 months) an increase of PSA levels emerged despite the ongoing ADT. The relationship between F-18-CH PET/CT findings and possible clinical predictors was investigated using both univariate and multivariate binary logistic regression analyses, including trigger PSA and ADT. Results Considering the whole population, overall DR of F-18-CH PET was 58.2 % (189/325 patients). In the whole sample of patients (group A), both at the univariate and multivariate logistic regression analysis, trigger PSA and ADT were significantly correlated with the DR of F-18-CH PET (p < 0.05). Moreover, the DR in patients under ADT (mean PSA 7.8 ng/ml) was higher than in patients not under ADT (mean PSA 3.9 ng/ml), (DR was 70.5 % and 48.9 %, respectively; p < 0.001), therefore, demonstrating the existence of a significant correlation between the DR of F-18-CH PET and ADT. In group B patients only trigger PSA resulted a reliable predictor of the F-18-CH positivity, since ADT was not correlated to the DR of F-18-CH PET (p = 0.061). Also in group B the DR of F-18-CH PET in patients under ADT was higher than in patients not under ADT (65.3 % and 51.3 %, respectively) but the difference was not significant without a statistically significant correlation in the Mann Whitney test (p = 0.456) therefore, suggesting the lack of correlation between DR F-18-CH PET/CT and ADT. Conclusion Similarly to previous published studies, in our series the overall DR of F-18-CH PET/CT was 58 % and was significantly correlated to trigger PSA. The most important finding of the present study is that ADT does not negatively influence DR of F-18-CH PET/CT in PC patients with biochemical relapse; therefore, it can be suggested that it is not necessary to withdraw ADT before performing F-18-CH PET/CT.