Circulating interleukin‐6 level is a prognostic marker for survival in advanced nonsmall cell lung cancer patients treated with chemotherapy

Abstract Lung cancer is the leading cause of cancer death worldwide as well as in Taiwan. Interleukin‐6 (IL‐6) is a multifunctional cytokine and has been implicated in tumor progression. This study recruited 245 patients with advanced (Stage 3B/4) nonsmall cell lung cancer (NSCLC) that had received chemotherapy, to evaluate associations between IL‐6 and lung cancer‐specific survival. Among these subjects, 112 gave blood samples before and 133 after the start of chemotherapy. Plasma IL‐6 was measured using an enzyme linked‐immunosorbent assay. The 33rd and 66th percentiles of IL‐6 concentrations were 2.01 and 25.16 for the 245 patients and were defined as the cutoff points for dividing the patients into low, intermediate and high groups. Kaplan‐Meier and Cox proportional‐hazard models were used to evaluate the relationship between the IL‐6 level and survival time. Results after adjusting for age, sex, smoking history, histologic type and stage of lung cancer revealed a significant relationship. For all patients, the hazard ratio with high IL‐6 levels for lung cancer‐specific survival was 2.10 [95% confidence interval (CI) = 1.49 − 2.96] compared with low IL‐6 levels. The hazard ratio for patients who were recruited before and after the start of chemotherapy was1.25 (95% CI = 0.73 − 2.13) and 3.66 (95% CI = 2.18 − 6.15), respectively. Patients with high circulating IL‐6 also responded poorly to chemotherapy. Therefore, a high level of circulating IL‐6 was associated with an inferior response and survival outcome in NSCLC patients treated with chemotherapy.