 The thymidylate synthase TS is an important target enzyme for antifolate drugs, such as 5-FUUFT and capecitabine,because it catalyzes an essential step in DNA synthesis. The predictive role of the expression of thymidylate synthase TS in tumors treated with antifolate drugs has been extensively reported in NSCLC.In 2006, Nakano et al performed an immunohistochemical study on the clinical significance of TS expression using 151 resected non-small-cell lung cancer NSCLC patients postoperatively treated with UFT.They found that the 5-year survival rate of patients with TS-negative tumours was significantly higher than that with TS-positive tumours P0.0133.Miyoshi et al reported that the oral administration of UFT after surgery might improve the survival of NSCLC patients when TS levels in tumor tissues are low,with the 5-year survival rates of patients positive and negative for TS were 50.0 and 89.5p0.001.Some research still found that TS expression was significantly higher in squamous cell carcinoma compared with adenocarcinoma when both mRNA levels and protein levels. 