Background: There is a need to develop novel therapies which could be beneficial to prostate cancer (CaP) patients including those who are predisposed to poor outcome such as African-Americans. This study investigates the role of ROBO1-pathway in predicting outcome and race-based disparity in CaP patients. Methods and Results:Aided by RNA sequencing-based DECIPHER-testing and IHC analysis of tumors we show that ROBO1 is lost during the progressive stages of CaP, a prevalent feature in African-Americans. We show that the loss of ROBO1 predicts high-risk of recurrence, metastasis and poor outcome of ADT