Purpose: The aim of this study was to assess the ability of fluorine-18-fluorocholine (F-FCH) PET/computed tomography (CT) to detect oligometastatic disease (OMD) in patients with early recurrence of prostate cancer (PC) [prostate-specific antigen (PSA)≤5 ng/ml].
Patients and methods: Between 2010 and 2016, 324 patients with PC and PSA levels of less than or equal to 5 ng/ml were recruited. The mean (SD) age of the patients was 71 (10) years. All patients were treated with a radical prostatectomy±lymphadenectomy. One-hundred and twenty-one patients were under hormonal therapy at the time of PET/CT, whereas 203 were not. The mean (SD) PSA at the time of PET/CT was 1.33 (1.19) ng/ml, the mean (SD) PSA doubling time (PSAdt) was 10 (12) months, and the mean (SD) PSA velocity (PSAvel) was 1.94 (3.31) ng/ml/year. The correlation between continuous and categorical data was assessed using Student's t-test or by analysis of variance and by the χ-test, respectively. Univariate and multivariate analysis was carried out for the identification of clinical variables able to predict the presence of OMD.
Results: One-hundred and ninety-three patients had a negative F-FCH PET/CT, whereas 131 (40.4%) had a positive scan. Of these latter patients, 35 had a significant F-FCH uptake in the prostatic fossae, 59 in the lymph nodes, and 37 in bone. PSA levels were significantly different between patients with a positive than those with a negative scan (P<0.001). F-FCH PET/CT was negative in the majority of patients with a PSA of less than or equal to 1 (63.2%) ng/ml. More than 60% of patients with a PSAdt of less than or equal to 6 months had a positive F-FCH PET/CT scan for OMD. PSAvel was higher in patients with a positive scan than those with a negative finding. At univariate analysis, PSA level, PSAdt, and PSAvel were predictors of a positive F-FCH PET/CT for OMD, whereas on multivariate analysis, only PSA level and PSAdt were independent predictors (both P<0.01). Furthermore, PSAdt was the only independent predictor of OMD at the lymph node level.
Conclusion: In patients with early recurrence of PC, F-FCH PET/CT is able to detect OMD in 40% of cases. This finding has an important impact on the detection of PC recurrent lesions that could be treated by local therapy to achieve long-term survival or cure.