Multimodality imaging using proton magnetic resonance spectroscopic imaging and 18F-fluorodeoxyglucose-positron emission tomography in local prostate cancer

AIM To assess the relationship using multimodality imaging between intermediary citrate/choline metabolism as seen on proton magnetic resonance spectroscopic imaging (1H-MRSI) and glycolysis as observed on 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) in prostate cancer (PCa) patients. METHODS The study included 22 patients with local PCa who were referred for endorectal magnetic resonance imaging/1H-MRSI (April 2002 to July 2007) and 18F-FDG-PET/CT and then underwent prostatectomy as primary or salvage treatment. Whole-mount step-section pathology was used as the standard of reference. We assessed the relationships between PET parameters [standardized uptake value (SUVmax and SUVmean)] and MRSI parameters [choline + creatine/citrate (CC/Cmax and CC/Cmean) and total number of suspicious voxels] using spearman's rank correlation, and the relationships of PET and 1H-MRSI index lesion parameters to surgical Gleason score. RESULTS Abnormal intermediary metabolism on 1H-MRSI was present in 21/22 patients, while abnormal glycolysis on 18F-FDG-PET/CT was detected in only 3/22 patients. Specifically, index tumor localization rates were 0.95 (95%CI: 0.77-1.00) for 1H-MRSI and 0.14 (95%CI: 0.03-0.35) for 18F-FDG-PET/CT. Spearman rank correlations indicated little relationship (ρ = -0.36-0.28) between 1H-MRSI parameters and 18F-FDG-PET/CT parameters. Both the total number of suspicious voxels (ρ = 0.55, P = 0.0099) and the SUVmax (ρ = 0.46, P = 0.0366) correlated weakly with the Gleason score. No significant relationship was found between the CC/Cmax, CC/Cmean or SUVmean and the Gleason score (P = 0.15-0.79). CONCLUSION The concentration of intermediary metabolites detected by 1H MRSI and glycolytic flux measured 18F-FDG PET show little correlation. Furthermore, only few tumors were FDG avid on PET, possibly because increased glycolysis represents a late and rather ominous event in the progression of PCa.