The combination of (13)N-ammonia and (18)F-FDG whole-body PET/CT on the same day for diagnosis of advanced prostate cancer

PURPOSE: The aim of the study was to evaluate the efficacy of (13)N-ammonia and (18)F-fluorodeoxyglucose ((18)F-FDG) PET performed on the same day in the detection of advanced prostate cancer (PC) and its metastases. PATIENTS AND METHODS: Twenty-six patients with high-risk PC [Gleason score 8–10 or prostate-specific antigen (PSA)>20 ng/ml or clinical tumor extension≥T2c] were recruited into the study. (13)N-Ammonia and (18)F-FDG PET/CT were performed on the same day ((18)F-FDG followed ammonia, with an interval of a minimum of 2 h). Lesions were interpreted as positive, negative, or equivocal. Patient-based and field-based performance characteristics for both imaging techniques were reported. RESULTS: There was significant correlation between (13)N-ammonia and (18)F-FDG PET/CT in the detection of primary PC (κ=0.425, P=0.001) and no significant difference in sensitivity (60.2 vs. 54.5%) and specificity (100 vs. 83.3%). The maximum standard uptake values and corresponding target-to-background ratio values of the concordantly positive lesions in prostate glands in the two studies did not differ significantly (P=0.124 and 0.075, respectively). The sensitivity and specificity of PET imaging using (13)N-ammonia for lymph node metastases were 77.5 and 96.3%, respectively, whereas the values were 75 and 44.4% using (18)F-FDG. The two modalities were highly correlated with respect to the detection of lymph nodes and bone metastases. CONCLUSION: The concordance between the two imaging modalities suggests a clinical impact of (13)N-ammonia PET/CT in advanced PC patients as well as of (18)F-FDG. (13)N-Ammonia is a useful PET tracer and a complement to (18)F-FDG for detecting primary focus and distant metastases in PC. The combination of these two tracers on the same day can accurately detect advanced PC.