Functional Imaging of Localized Prostate Cancer Aggressiveness Using 11C-Acetate PET/CT and 1H-MR Spectroscopy

We assessed the ability of C-11-acetate PET/CT, MRI, and proton MR spectroscopy (H-1-MRS) to image localized prostate cancer and detect its aggressiveness, using qualitative and quantitative approaches. Methods: Twenty-one patients with untreated localized prostate cancer, diagnosed using transrectal ultrasound-guided biopsy, were prospectively enrolled. Cancer laterality was based on the percentage of cancer and the highest Gleason score determined from biopsies. In addition to PET/CT, 3-dimensional H-1-MRS of the entire prostate volume using a quantitative approach was performed. The imaging and histologic findings of 8 patients undergoing subsequent prostatectomy were compared on a sextant level. For each lobe and sextant, standardized uptake values (SUVs) and (choline + creatine + polyamines)-to-citrate (CCP/C) ratios were obtained from C-11-acetate PET/CT and H-1-MRS, respectively. The visual and quantitative findings on PET/CT and MRI data were compared with cancer laterality and aggressiveness based on the Gleason score and with prostate-specific antigen (PSA) velocity and international risk group classification. Results: The sensitivity, specificity, and accuracy, on a lobar level using visual analysis, of C-11-acetate PET/CT were 80%, 29%, 71%, respectively, and 89%, 29%, 79%, respectively, using contrast-enhanced MRI. The sensitivity and accuracy of C-11-acetate PET/CT decreased to 64% and 63% and specificity increased to 62% when sextant analysis was performed. The agreement between prostate cancer laterality based on biopsy findings and visual interpretation of C-11-acetate PET/CT and contrast-enhanced MRI was similar at 71%. The mean SUV maximum and CCP/C maximum for the dominant tumor lesion were 5.5 and 1.48, respectively, and did not differ significantly from values in the nondominant lobe. The dominant-lesion SUVs or CCP/C values were not associated with histologically determined prostate cancer aggressiveness, nor did PSA velocity correlate with the SUV or CCP/C values from the entire gland. Conclusion: C-11-acetate PET/CT, MRI, and H-1-MRS enable detection of localized prostate cancer with comparable and limited accuracy but fail to provide information on cancer aggressiveness.