Background: In advanced colorectal cancer (CRC) a low expression of thymidylate synthase (TS) in metastases predicts a higher response to 5-fluorouracil (5-FU). The purpose of this study was to investigate the expression of TS in liver and lung metastases of CRC and their matched primary tumours.
Patients and methods: Immunohistochemical analysis of TS expression was performed on tissue samples of 48 CRC metastases (liver n=38, lung n=10) and their matched primary tumours (n=45).
Results: There was no significant correlation between TS expression in 33/48 (69%), matched samples of metastases and primary tumours (r=0.02, p=1.0).
Conclusion: This study indicates that TS expression in liver and lung metastases of CRC does not always reflect the level of TS in their corresponding primary tumours. Therefore, it might not be accurate to solely rely on analyses of TS in the primary tumours to predict the effect of 5-FU-based chemotherapy in metastatic CRC.