Pretreatment serum interleukin-6 concentration as a prognostic factor of overall survival in metastatic malignant melanoma patients treated with biochemotherapy: a retrospective study

Abstract

Biological response parameters during biochemotherapy, including chemotherapy with immune modulating agents, have been studied extensively. Of these parameters, interleukin-6 (IL-6) has been implicated in advanced stage disease and tumour recurrence. However, there is limited information available about the significance of IL-6 in metastatic malignant melanoma (MMM). In this study, we evaluated the possible relationship between serum IL-6 level and overall survival. This retrospective study included 125 patients with MMM. Pretreatment serum IL-6 levels were determined using a highly sensitive enzyme-linked immunosorbent assay (ELISA) test. Kaplan-Meier survival curves were constructed and compared using the log-rank test. Cox proportional analysis was performed to assess the predictors of overall survival, which was calculated from the beginning of biochemotherapy until death. In order to establish the possible relationship between IL-6 level and overall survival, patients were divided into two groups according to a cut-off of 5 pg/ml, corresponding to the first quartile obtained by descriptive statistics of the pretreatment IL-6 level in all patients. Thirty-five patients were in the low IL-6 group and 76 patients were in the high IL-6 group. Based on this stratification, overall survival was shown to be affected by IL-6 serum level: it was higher (24.6 months) in the low IL-6 group when compared with the high IL-6 group (9.7 months) (P=0.0006). Furthermore, Cox multivariate analysis including standard melanoma prognostic factors showed that IL-6, as a variable, lactate dehydrogenase (LDH) and tumour burden were significant prognostic factors for overall survival. On the basis of this evidence, the pretreatment serum IL-6 level is a predictive factor of overall survival in MMM.