Immunologic Correlates of the Abscopal Effect in a Patient with Melanoma
Summary
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 monoclonal 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.)
The abscopal effect refers to a rare phenomenon of tumor regression at a site distant from the primary site of radiotherapy.1 Localized radiotherapy has been shown to induce abscopal effects in several types of cancer, including melanoma, lymphoma, and renal-cell carcinoma.2–4 The biologic characteristics underlying this effect are not completely understood, but it may be mediated by immunologic mechanisms.5
NY-ESO-1 is an antigen expressed in 30 to 40% of patients with advanced melanoma but not present in normal adult tissues except testicular germ cells and placenta.6 Ipilimumab (Bristol-Myers Squibb) has been shown to enhance immunity to NY-ESO-1, and patients with preexisting NY-ESO-1 antibodies have an increased likelihood of benefiting from ipilimumab.7 We describe a patient with metastatic melanoma in whom we measured changes in NY-ESO-1 titers before and during the observed abscopal effect.
Inducible costimulator (ICOS) is a marker of activated T cells. Increases in CD4+ ICOShigh cells have been associated with clinical benefit from ipilimumab.8 We assessed the frequency of this cell population in the patient's peripheral blood. We also measured interferon-γ–producing CD8+ and CD4+ T cells and myeloid-derived suppressor cells (defined as CD14+ HLA-DRlow),9 which contribute to tumor-induced immunosuppression, perhaps by limiting activated T-cell entry into the tumor site.10 Finally, we investigated changes in humoral immune responses before and after radiotherapy to a panel of antigens to discover additional antigenic targets potentially relevant to antitumor immunity, a process referred to as seromics.11
https://www.ncbi.nlm.nih.gov/pmc/articl ... po=1.31579