Three cases of nivolumab therapy-failed advanced melanoma successfully controlled by ipilimumab with intensity-modulated radiotherapy.

Anti-programmed death 1 antibody monotherapy is a first-line and widely used immunotherapy for the treatment of advanced melanoma. However, its efficacy rate is lower in the Japanese population compared with the Caucasian population. Ipilimumab is another immune checkpoint inhibitor (ICI) that activates and increases T cells, which suppress the function of regulatory T cells. Previous reports have suggested that ipilimumab is useful for treating advanced melanoma, particularly in combination with radiation therapy. In this report, we described three cases of nivolumab-resistant melanoma successfully controlled by ipilimumab with intensity-modulated radiotherapy, which may enhance the therapeutic effects of the sequential administration of ICI.