The prognosis of advanced metastatic melanoma remains poor although a breakthrough has been achieved with the novel anti-CTLA-4 treatment (ipilimumab) for a subset of patients. Unfortunately, due to immune resistance, the majority of patients do not obtain long-lasting clinical benefit. Radiotherapy is able to interfere with immune resistance by inducing immunogenic cell death. Preclinical evidence indicates that combining radiotherapy with anti-CTLA-4 treatment increases response rates compared to single agent treatment. These data are supported by several spectacular clinical cases and one retrospective study. The investigators hypothesize that combining ipilimumab with radiotherapy will result in a higher response rate compared to ipilimumab or radiotherapy in monotherapy. Given the complexity of the interaction in anti-tumor immunity, the first goal of this project is to assess the safety of the combined treatment.