Elevated serum CRP levels after induction chemoradiotherapy reflect poor treatment response in association with IL‐6 in serum and local tumor site in patients with advanced esophageal cancer

Abstract

Elevated serum CRP levels are associated with tumor progression and poor prognosis of esophageal cancer. The aim of this study was to clarify the clinical significance of CRP in relation to response to chemoradiotherapy in patients with esophageal cancer. The relationship between serum CRP levels and response to chemoradiotherapy and prognosis was analyzed in 34 patients with advanced esophageal squamous cell carcinoma who underwent induction chemoradiotherapy followed by surgery. The relationship between response to chemoradiotherapy and interleukin-6 (IL-6) expression in sera and tumor tissues was also analyzed. Although elevated serum CRP levels were associated with poor response to chemoradiotherapy, significant difference in CRP levels between pathological responders (n = 18) and non-responders (n = 16) was observed after chemoradiotherapy, but not before. Patients with elevated CRP levels had shorter cause-specific survival, but significant difference was observed only after chemoradiotherapy. In addition, serum levels of IL-6 were also associated with poor treatment response following chemoradiotherapy and were correlated with residual tumor volume. IL-6 expression was detected in residual tumor tissues by immunohistochemistry. Elevated serum CRP levels after chemoradiotherapy may predict poor response to chemoradiotherapy more accurately than before chemoradiotherapy, and IL-6 may be a possible target associated with chemoradiotherapy resistance.