Serum Immunoregulatory Proteins as Predictors of Overall Survival of Metastatic Melanoma Patients Treated with Ipilimumab

Treatment with ipilimumab improves overall survival (OS) in patients with metastatic melanoma. Because ipilimumab targets T lymphocytes and not the tumor itself, efficacy may be uniquely sensitive to immunomodulatory factors present at the time of treatment. We analyzed serum from patients with metastatic melanoma (247 of 273, 90.4%) randomly assigned to receive ipilimumab or gp100 peptide vaccine. We quantified candidate biomarkers at baseline and assessed the association of each using multivariate analyses. Results were confirmed in an independent cohort of similar patients (48 of 52, 92.3%) treated with ipilimumab. After controlling for baseline covariates, elevated chemokine (C-X-C motif) ligand 11 (CXCL11) and soluble MHC class I polypeptide-related chain A (sMICA) were associated with poor OS in ipilimumab-treated patients log10 CXCL11: HR, 1.88; 95% confidence interval (CI), 1.14-3.12; P = 0.014; and log10 sMICA quadratic effect P = 0.066; sMICA (≥ 247 vs. 247): HR, 1.75; 95% CI, 1.02-3.01. Multivariate analysis of an independent ipilimumab-treated cohort confirmed the association between log10 CXCL11 and OS (HR, 3.18; 95% CI, 1.13-8.95; P = 0.029), whereas sMICA was less strongly associated with OS log10 sMICA quadratic effect P = 0.16; sMICA (≥ 247 vs. 247): HR, 1.48; 95% CI, 0.67-3.27. High baseline CXCL11 and sMICA were associated with poor OS in patients with metastatic melanoma after ipilimumab treatment but not vaccine treatment. Thus, pretreatment CXCL11 and sMICA may represent predictors of survival benefit after ipilimumab treatment as well as therapeutic targets.