Working Out M0 Bipolar Androgen Therapy

This is a study to assess the efficacy and safety of cyclical testosterone and darolutamide in non-metastatic castration-resistant prostate cancer. Adults with castrate resistant prostate cancer, with no evidence of metastatic disease (M0) on conventional imaging \[Whole Body Bone Scan (WBBS) and Computed Tomography (CT) scan at screening\] and prostate specific antigen (PSA) only progression on darolutamide may be eligible. Study participants will receive cyclical treatment with intramuscular (IM) testosterone, darolutamide and ongoing medical/surgical castration. This will be delivered in 56-day cycles until evidence of metastatic disease on conventional imaging unless treated beyond progression. Participants will be asked to provide blood samples, complete questionnaires and undergo scans during their treatment. It is hoped that findings from this study will help develop new treatment pathways for those with non-metastatic castration-resistant prostate cancer.