For many men, prostate cancer is diagnosed when it is slow-growing or indolent, and outcome of these patients is often very good. However, for other men with aggressive disease, prognosis is poor. This is primarily due to metastasis, which occurs when tumor cells spread from the prostate to other organs in the body. Therefore, one of the major clinical challenges in prostate cancer is differentiating between those patients who will have indolent versus aggressive prostate cancer in order to ensure that the most appropriate/effective treatment is provided. Research in the Allan lab focuses on developing tests that identify circulating tumor cells (CTCs) in a patient’s blood as a biomarker of aggressiveness and/or metastasis. Their recent work has been focused on advanced castrate resistant prostate cancer (CRPC), with excellent success. However, Dr. Allan and her team believe that CTC tests that can help differentiate between slow-growing versus aggressive prostate cancer should also be developed. The goal of this proposal is evaluate a new CTC assay called VyCAP using pre-clinical mouse models that have been engineered to have either slow-growing or aggressive prostate cancer. Successful completion of this study will allow this CTC test to move into early clinical studies to test its effectiveness in patients.