IL-6 and MCP-1 genetic polymorphisms are predictive of decreased platelet counts caused by chemoradiotherapy in esophageal cancer

Background A reliable marker of the sensitivity of esophageal cancer to chemoradiotherapy (CRT) as well as a personal biomarker predictive of adverse events during treatment has long been sought. The purpose of the present study was to test whether there is an association between interleukin-6 (IL-6) and/or monocyte chemoattractant protein-1 (MCP-1) polymorphisms and CRT-induced bone-marrow suppression––i.e., reductions in white blood cell and/or platelet counts. Methods The study participants were 103 Japanese patients treated with definitive or pre-operative CRT for squamous cell esophageal cancer at Akita University Hospital. The patients were divided into two groups, with or without adverse events during or up to 1 month after CRT. Results Patient backgrounds––i.e., white blood cell and platelet counts before CRT and doses of chemotherapy and irradiation––did not differ between groups. However, there was a significantly higher incidence of grade 2–4 platelet count reductions (<75,000/mm 3 ) among patients carrying the IL-6 −634C/G+G/G genotype than among those carrying the C/C genotype. Similarly, there was a significantly higher incidence of grade 2–4 platelet count reductions among patients carrying the MCP-1 −2518G/G genotype than among those carrying the A/A+A/G genotype. Univariate and multivariate logistic regression models revealed that the IL-6 −634C>G and MCP-1 −2518A>G polymorphisms were significantly associated with grade 2–4 platelet count reductions following CRT. Conclusion These polymorphisms may thus be clinically relevant and should be taken into consideration when devising CRT regimens or treatment strategies for esophageal cancer.