Thymidylate synthase expression and prognosis in colorectal cancer: a meta-analysis of colorectal cancer survival data

Background: Although many studies have investigated the prognostic effect of thymidylate synthase (TS) in colorectal cancer, no consensus has been reached. The aim of this meta-analysis was to obtain a more precise estimate of the prognostic significance of TS expression in localized cancers treated by curative resection and adjuvant chemotherapy. Materials and method: Seventeen eligible studies reporting survival in 2,893 patients stratified by TS expression were pooled using a fixed- or random-effects model. The main outcome measure was hazard ratio (HR). Results: The overall HR for overall survival was 1.01 (95% CI 0.74-1.39, p= 0.947), with an I-2 of 64.4%. The total HR for disease-free survival was 1.36 (95% CI 0.97-1.89, p= 0.072), with an I2 of 75.8%. In the TS protein-tested subgroup, the total HR for disease-free survival was 1.72 (95% CI 1.02-2.89, p= 0.042),with an I-2 of 81.3%. Conclusion: Our meta-analysis showed that, in the adjuvant setting, TS expression does not predict a poorer disease-free survival or a worse overall survival. Therefore, we believe that it is inappropriate to regard TS expression as a prognostic factor for patients with stage II and stage III colorectal cancer treated by surgery and adjuvant chemotherapy.