Abstract: Objective To investigate the expression of thymidylate synthase (TS), and the correlations with the clinicopathologcal factors and the prognosis of postoperative fluorouracil chemotherapy in gastric cancer. Methods 42 patients with gastric cancer who underwent radical gastrectomy were collected from April 2011 to April 2014 in Lu′an Hospital of Anhui Medical University, and the chemotherapy regimen was Cisplatin+Capecitabine or Cisplatin+Teggio. The levels of TS in tumor tissues of 42 patients with gastric cancer were detected by immunohistochemical method. The relationships between TS expression level, clinical features and the prognosis of patients treated with fluorouracil chemotherapy were analyzed. Results In 42 patients with gastric cancer, 19 patients (45.2%) have TS high expressions, 23 patients (54.8%) have TS low expressions. There were no significant correlations between the expression of TS and age, sex, clinical stage, differentiation degree, tumor location, depth of invasion, lymph node metastasis, vascular tumor thrombus and nerve bundle invasion (all P＞0.05). There were significant differences between low TS expression and high TS expression in median progression-free survival and 3-year survival rate of patients ［35 months vs. 17 months, 73.9% (17/23) vs. 42.1% (8/19)］, and the differences were statistically significant (χ2=4.788, P=0.029; χ2=4.369, P=0.037). In patients with stage Ⅲ gastric cancer, the median progressionfree survival of patients with low TS expression was significantly prolonged compared to that with high TS expression (33 months vs. 9 months), and the difference was statistically significant (χ2=4.731, P=0.030). Conclusion TS expression levels have no significant correlations with the clinicopathologcal factors, but closely relate to the prognosis of gastric cancer patients treatment with fluorouracil chemotherapy. The chemotherapy prognosis of TS high expression   is worse than that of TS low expression in gastric cancer.

Key words: Thymidylate synthase, Stomach neoplasms, Chemotherapy, adjuvant, Fluorouracil