C-Acetate PET/CT Imaging to Evaluate Treatment Changes in Prostate Cancer

Our proposed study aims to use 11C-acetate PET/CT for evaluation of treatment response to Ra-223 dichrolide therapy. 11C-acetate has been shown to have superior detection of osseous and non-osseous metastatic lesions as compared to 18F-FDG PET/CT and 99Tc-MDP imaging. 11C-acetate is generally \>80% sensitive for detection of metastatic lesions as compared to less than 70% for 18F-FDG PET/CT with higher tumor than tumor to background ratio14-19. The majority of interest in 11C-acetate PET/CT imaging is focused on the detection of distant metastatic disease in patients with biochemical relapse status post definitive local therapy18,20,21. In patients with 99Tc-MDP detected prostate bone metastases, Yu et al. have found that 11C-acetate PET/CT was superior to 18F-FDG PET/CT for evaluation of bone metastases treatment response regardless of hormonal or taxol based chemotherapy. In the Yu et al. pilot study, 11C-acetate PET/CT findings correlated with composite clinical designation of treatment response in 100% of patients22. Our study will evaluate baseline standard uptake value (SUVmax) and change in SUVmax of 11C-acetate PET/CT at approximately 10 weeks weeks (+/- 3 weeks) , generally after two cycles of Ra-223 dichloride therapy. SUVmax will be recorded for a selected index lesion and an average of the 5 most 11C-acetate avid lesions, from the baseline scan. Evaluation of 11C-acetate uptake changes to therapy in this pilot study will allow sample size calculation for future trials correlating 11C-acetate changes to therapy to TTP, OS and symptomatic relief end points.