RÉSUMÉ
Objective Currently , the targeted therapy is the first-choice treatment of advanced non-small cell lung cancer (NSCLC) in with epidermal growth factor receptor (EGFR) mutations, but few studies have been reported on the relationship between immunohistochemical markers and the EGFR mutation.The aim of this study is to analyze the relationship of the EGFR mutation with the ex-pressions of thymidylate synthetase (TS), excision repair cross-com-plementation group 1 ( ERCC1 ) , β-tubulin-III, and ribonucleofide reductase large subunit-l ( RRM1) in NSCLC. Methods We retro-spectively analyzed 336 cases of NSCLC treated in the Department of Medical Oncology , the Affiliated Hospital of Inner Mongolia Medical University, from June 2014 to December 2015 and examined 29 EGFR mutations.We divided the patients into a mutation and a non-mutation group, performed immunohistochemical staining of the TS, ERCC1,β-tubulin-III and RRM1 proteins and compared their expressions in the NSCLC tissue between the two groups . Results EGFR mutations were found in 138 ( 41.07%) of the 336 NSCLC patients but not in the other 198 ( 58.93%) .The expression of TS was significantly lower in the mutation than in the non-mutation group (9.42%vs 39.39%, P<0.05), and so was that of β-tubulin-III (44.2%vs 60.1%, P<0.05).EGFR mutations were correlated with decreased expressions of TS (r=-0.332, P<0.05) andβ-tubulin-III (r=-0.157, P<0.05).Multivariate regression analysis showed that the risk of EGFR mutations was 2.109 times higher in the fe-male patients than in the males (OR=2.109, 95%CI:1.268-3.509), 24.265 times higher in the adenocarcinoma than in the adeno-squamous carcinoma patients (OR=24.265, 95%CI:3.508-167.845), 15.2 times higher in the squamous carcinoma than in the ade-nocarcinoma patients (OR=15.200, 95%CI:4.480-51.569), 2.364 times higher in the lung biopsy specimens than in the surgically treated patients (OR=2.364, 95%CI:1.266-4.413), and 6.171 times higher in the patients with lowly expressed than in those with highly expressed TS (OR=6.171, 95%CI: 3.145-12.109). Conclusion The decreased expressions of TS and β-tubulin-Ⅲ in NSCLC indicate the mutation of the EGFR gene.