In the era of PET imaging, many sites of disease that are not visible on conventional imaging will be found on PSMA (prostate specific membrane antigen) PET. For men with castration-resistant prostate cancer with no evidence of metastases on conventional imaging but detectable disease on Prostate Specific Membrane Antigen (PSMA)-PET/CT scan, DECREASE will compare the treatment outcomes of men taking Darolutamide with or without treating the small metastasis seen on the PSMA PET scan with radiation therapy. Lead by A/Profs Shankar Siva and Arun Azad, DECREASE aims to determine that the combination (Darolutamide + RT) is better than Darolutamide alone at controlling PSA levels and further spread of prostate cancer.