Immunologic Correlates of the Abscopal Effect in a Patient with Melanoma

The abscopal effect is a phenomenon in which local radiotherapy is associated with the regression of metastatic cancer at a distance from the irradiated site. The abscopal effect may be mediated by activation of the immune system. Ipilimumab is a mono‑ clonal antibody that inhibits an immunologic checkpoint on T cells, cytotoxic T‑lymphocyte–associated antigen 4 (CTLA ‑ 4). We report a case of the abscopal effect in a patient with melanoma treated with ipilimumab and radiotherapy. Temporal associations were noted: tumor shrinkage with antibody responses to the cancer– testis antigen NY‑ ESO‑ 1, changes in peripheral‑ blood immune cells, and increases in antibody responses to other antigens after radiotherapy. (Funded by the National Institutes of Health and others.)