Metastatic spread of cancer from its primary site to distant organs is the commonest cause of death from cancer. The term oligometastases describes an intermediate metastatic state, in which cancer exists as a limited number of metastases at first, before cells acquire the ability to metastasise more widely. For the large majority of solid cancers, once metastatic disease has been diagnosed the chances of cure are small. There are several situations where this is not the case, but it is not known if stereotactic body radiotherapy (SBRT) for oligometastatic disease will alter outcomes or whether the toxicity burden of this treatment is justified. SBRT is targeted radiotherapy which destroys cancer cells in the area of the body it is aimed at however low dose radiation may be received by surrounding tissue.