The effects of thymidylate synthase (TS) polymorphisms on susceptibility to colorectal cancer (CRC) have been investigated in many studies, but the results remain conflicting rather than conclusive. To resolve these conflicts, we performed a quantitative synthesis of the evidence on the association between these two polymorphisms and CRC risk.

All eligible case-control studies published up to September 2013 were identified by searching PubMed, Web of Science and CNKI. Effect sizes of odds ratio (OR) and 95% confidence interval (95% CI) were calculated by using a fixed- or random-effect model.

A total of 11 case-control studies were included, including 10 studies (3324 cases and 4622 controls) for TSER polymorphism and 9 studies (3223 cases and 3886 controls) for TS1494del6 polymorphism. Overall, no significant association between the TS polymorphisms and CRC risk was found. In the subgroup analysis by ethnicity, a significantly association were found among Caucasian populations for TSER polymorphism; but for TS1494del6 polymorphism, no significantly association was observed in both Asian and Caucasian populations. When stratifying by source of controls, we found there was a statistically significant association between TSER polymorphism and risk of CRC in the population-based population; however, we detected no association in both population-based and hospital-based populations for TS1494del6 polymorphism.

This meta-analysis suggests that the TSER polymorphism in TS gene but not TS1494del6 polymorphism might be a protective factor for CRC among Caucasian populations.