Sean S. Park, M.D., Ph.D.

Success of cancer immunotherapy is limited by the ability of solid tumors to evade local and systemic antitumoral immune responses. Several mechanisms of tumor immune evasion have been identified, including low intratumor expression of antigens and elevated expression of inhibitory co-regulatory molecules. An effective immunotherapy is one which would induce necrotic cell death and accompanying proinflammatory cytokine induction. Stereotactic Body Radiotherapy (SBRT) or Intensity Modulated Radiotherapy (IMRT) or brachytherapy, which is capable of delivering high, confromal radiation doses (>8 Gy) of tumor ablative radiation may be an effective means of conditioning a tumor bed to a state favorable to the initiation of robust antitumoral immune responses.

Castration-resistant prostate cancer patients with rising prostatic specific antigen (PSA) are eligible for this study. 11C-Choline PET/CT will be used to identify metastatic lesions. Patients with <=3 metastatic lesions will receive stereotactic body radiotherapy (SBRT) as definitive treatment. Blood draws will be taken to monitor the development of anti-prostate cancer immunity

Patients will be imaged with MRE at the time of the RT planning MRI, prior to the induction of RT and immunotherapy. Research imaging will be in addition to standard imaging studies performed at time points consistent with the standard of care (at the time of the RT planning MRI and the first clinical follow-up). An additional MRE exam will be performed at the end of treatment outside the standard of care imaging.