Interleukin-6 blood level is associated with circulating carcinoembryonic antigen and prognosis in patients with colorectal cancer

Background: Interleukin-6 (IL-6) is an important proinflammatory cytokine t hat has multiple effects on stimulating inflammation and cell growth. Exper imental data suggest that carcinoembryonic antigen (CEA) induces the system ic production of IL-6 and that IL-6 may stimulate tumor cell growth at meta static sites. We tested the hypothesis that blood concentrations of IL-6 ar e associated with the amount of circulating CEA and with prognosis in patie nts with colorectal cancer. Methods: CEA and IL-6 concentrations were measured by using enzyme immunoas say in preoperative serum samples from 208 patients with stages I through I V colorectal cancer. Results: Linear regression analysis showed a significant association betwee n serum values of CEA and IL-6 (r = .544; R-2 = .296; P < .001). Patients w ith stage III and stage IV disease had a significantly higher IL-6 serum co ncentration than those with stage I and stage II disease. In patients with stages I through III, 5-year survival was 83% in cases with concentrations of IL-6 at 10 pg/ml or less (n = 94) and 56% in cases with IL-6 concentrati ons of more than 10 pg/ml (n = 54; P = .001; median follow-up time, 46 mont hs). By using multivariate analysis, an IL-6 concentration of more than 10 pg/ml was an independent prognostic factor of survival (relative risk = 1.8 20; P = .020). Conclusions: In patients with colorectal cancer, blood concentration of IL- 6 is associated with high circulating CEA and advanced stage. Furthermore, an IL-6 concentration of more than 10 pg/ml is an independent negative prog nostic marker of survival.