Background: Although the clinical outcome of esophageal cancer has recently improved, the relapse rate remains high for all disease stages. At present, there is no diagnostic method to predict the long-term outcome for esophageal cancer. In this study, we evaluated serum preoperative proinflammatory cytokine levels and investigated the correlation between preoperative interleukin-6 (IL-6) and IL-8 levels and survival of patients with esophageal cancer. Methods: Between 2008 and 2015, we evaluated preoperative serum cytokine levels in 122 patients who underwent esophagectomy for esophageal cancer. Serum IL-6 and IL-8 levels were measured by enzyme-linked immunosorbent assays. We investigated the relationship between serum cytokine levels and the response to chemotherapy and survival. Results: The preoperative IL-6 levels were significantly associated with shorter recurrence-free survival (RFS, p = 0.001) and overall survival (OS, p = 0.001) after esophagectomy. Higher IL-8 levels were significantly associated with RFS (p = 0.018). In the multivariate analysis, age, preoperative chemotherapy, lymph node metastasis, serum C-reactive protein (CRP) levels and serum IL-6 levels (hazard ratio (HR), 2.888; p = 0.049) were significantly independent prognostic factors of RFS. Additionally, age, pathological stage, and serum IL-6 levels (HR, 3.247; p = 0.027) were shown to be significantly independent prognostic factors of OS. Serum IL-6 levels were significantly higher in the non-responder group (pathological response pGrade0 and pGrade1) after neoadjuvant therapy. Conclusions: High preoperative serum IL-6 levels are associated with a poor response to chemotherapy or chemoradiotherapy and poor prognosis after esophagectomy. Preoperative serum IL-6 levels may be a useful independent prognostic marker for esophageal cancer patients.
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