In patients with metastatic prostate cancer (PCa) who receive androgen deprivation therapy (ADT), the sensitivity to castration will eventually disappear due to the selection of castration-refractory clones. This will lead to the stage of metastatic castration-refractory prostate can-cer (mCRPC), which is incurable and results in a median overall survival of 2-3 years. Treatment options for patients with mCRPC include several systemic agents, such as andro-gen receptor-targeted agents (ARTA), chemotherapy (docetaxel, cabazitaxel) and bone-targeting agents (radium- 223). Clinical progression and, to a lesser extent, biochemical pro-gression traditionally imply a switch to the next line systemic treatment (NEST). Within patients with mCRPC, there is a subgroup showing oligo-progression, defined as the progression of up to 3 lesions, including both metastatic and/or local relapse. Oligoprogression reflects a heterogeneous treatment response, which, in turn, reflects the heterogeneity of the clonogenic cells that give rise to mCRPC. Retrospective studies suggest that metastasis-directed radiotherapy (MDRT) to these oligoprogressive lesions delayed the need for NEST. Recently, promising results were published on the use of MDRT in the oligopro-gressive mCRPC (omCRPC) setting, with a NEST-free survival (NEST-FS) of 21 months in well selected patients. Currently, in The Netherlands, patients with omCRPC are frequently referred and treated with MDRT, but a clear treatment protocol and inclusion/selection criteria are missing. Moreover, the exact benefit of MDRT in patients with omCRPC remains unclear, as prospective evi-dence for MDRT in omCRPC is lacking.