Data from Topical TLR7 Agonist Imiquimod Can Induce Immune-Mediated Rejection of Skin Metastases in Patients with Breast Cancer

Abstract

<div>Abstract<p><b>Purpose:</b> Skin metastases of breast cancer remain a therapeutic challenge. Toll-like receptor 7 agonist imiquimod is an immune response modifier and can induce immune-mediated rejection of primary skin malignancies when topically applied. Here we tested the hypothesis that topical imiquimod stimulates local antitumor immunity and induces the regression of breast cancer skin metastases.</p><p><b>Experimental Design:</b> A prospective clinical trial was designed to evaluate the local tumor response rate of breast cancer skin metastases treated with topical imiquimod, applied 5 d/wk for 8 weeks. Safety and immunologic correlates were secondary objectives.</p><p><b>Results:</b> Ten patients were enrolled and completed the study. Imiquimod treatment was well tolerated, with only grade 1 to 2 transient local and systemic side effects consistent with imiquimod's immunomodulatory effects. Two patients achieved a partial response [20%; 95% confidence interval (CI), 3%–56%]. Responders showed histologic tumor regression with evidence of an immune-mediated response, showed by changes in the tumor lymphocytic infiltrate and locally produced cytokines.</p><p><b>Conclusion:</b> Topical imiquimod is a beneficial treatment modality for breast cancer metastatic to skin/chest wall and is well tolerated. Importantly, imiquimod can promote a proimmunogenic tumor microenvironment in breast cancer. Preclinical data generated by our group suggest superior results with a combination of imiquimod and ionizing radiation and we are currently testing in patients whether the combination can further improve antitumor immune and clinical responses. <i>Clin Cancer Res; 18(24); 6748–57. ©2012 AACR</i>.</p></div>