Analysis of the Effect of Serum Interleukin-6 (IL-6) and Soluble IL-6 Receptor Levels on Survival of Patients with Colorectal Cancer

Objective The correlations of serum interleukin-6 and soluble interleukin-6 receptor concentrations with clinicopathological features and survival of patients with colorectal cancer were studied. Methods We measured the serum levels of interleukin-6 and soluble interleukin-6 receptor in 99 colorectal cancer patients at the Chang Gung Memorial Hospital, Taiwan. The interleukin-6 and soluble interleukin-6 receptor levels were tested for their association with each other, and with the clinical parameters and outcomes. Results Both interleukin-6 and soluble interleukin-6 receptor concentrations were significantly higher in colorectal cancer patients than in normal individuals. Unlike patients with serum interleukin-6 levels >10 pg/ml, who have increased carcinoembryonic antigen levels and shorter survival, serum soluble interleukin-6 receptor levels >800 pg/ml were found in patients with stages I–II and no regional lymph nodal invasion and appeared to be a positive prognostic factor for improved survival. Especially, patients with serum interleukin-6 800 pg/ml lived significantly longer. Nonetheless, the multivariate analysis showed that only tumor-node metastasis stage, metastatic status and serum interleukin-6 level were independent prognostic factors, whereas the serum soluble interleukin-6 receptor level became marginally important for survival. Conclusions We suggest the clinical relevance of interleukin-6 and soluble interleukin-6 receptor for the survival of colorectal cancer patients. From a practical point of view, detection of the serum interleukin-6 level alone, rather than combined measurement of interleukin-6 and soluble interleukin-6 receptor, may be sufficient to independently predict survival in colorectal cancer patients.