Surgery is the standard treatment for primary kidney cancer, however, in some cases surgery is either not possible or other health problems make surgery high risk. This study involves a relatively new, highly precise multidirectional radiotherapy technique called Stereotactic Ablative Body Radiotherapy (SABR) and all participants will receive this radiotherapy technique. The aim of the study is to test the ability of this technique to control the cancer within the kidney for those people where surgery is not an option, as well as to examine the side effects of the treatment, including how it may affect your kidney’s function.