Changes in T cell immunity in patients with metastatic castration resistant prostate treated with Radium-223 treatment.

295 Background: The bone seeking calcium mimetic, Radium223 (Ra223), emits high energy alpha particle that cause irreparable double strand DNA breaks in osseous metastases. Ra223 improves survival in patients with bone-predominant metastatic castration resistant prostate cancer (mCRPC). The effect of Ra223 on the host immune system, and T cell immunity in particular, is unknown. Methods: Eligible patients include men with mCRPC, osseous metastases and a clinical indication for Ra223 were eligible. Blood samples were collected at the following time points: prior to the first, second, and fourth treatments (tx) and 4 weeks after the sixth dose. Peripheral blood mononuclear cells (PBMCs) were purified and stained with a cocktail of antibodies to surface and effector immune molecules. Some PBMCs were stimulated and stained for intracellular cytokines (IFN-g, TNF-a, IL-13, IL-17, and IL-21). Stained cells were analyzed by flow cytometry. Results: A total seven patients completed at least two sample collections...