While many prostate cancers are diagnosed at an early stage, our limited diagnostic tools prevent us from answering the simplest clinical questions: How dangerous is my cancer, and does it require aggressive treatment? Given that metastasis, or the spread of cancer, is responsible for more than 90% of prostate cancer deaths, it is critical that we develop new tests that can predict the risk of cancer metastasis. In this project, we will utilize a recently developed blood test called EV-FPS that seems to predict how cancer will progress. We will evaluate the use of this test in a clinical laboratory environment to see if it improves significantly on the current PSA test. This should provide more reliable information about how dangerous a patient’s cancer is so that an appropriate treatment decision can be made.