Differential Expression of Thymidylate Synthase in Colorectal Tumors and Matched Lymph Nodes: Impact on Adjuvant Treatment

This is the authors' abstract. We don't add key points for this paper.

Although the expression of thymidylate synthase (TS) in metastatic colorectal cancer (CRC) may be a better predictor of response to 5-fluorouracil chemotherapy than TS expression in primary CRC, this enzyme has not been well studied in tumor-draining regional lymph nodes. We retrospectively examined TS expression in 12 primary CRC lesions (pT3) and matched sentinel lymph nodes. Of the 8 primary tumors that were TS-positive, 50 per cent (4/8) had tumor-positive lymph nodes and 50 per cent (4/8) had tumor-negative nodes. Of the 4 primary tumors that were TS-negative, 75 per cent (3/4) had tumor-positive nodes and 25 per cent (1/4) had tumor-negative nodes [kappa = -0.1386, 95 per cent confidence interval: (-0.4820, 0.2048), P = 0.4284]. Of the 8 TS-positive primaries, 25 per cent (2/8) had TS-positive nodes and 75 per cent (6/8) had TS-negative nodes. Of the 4 TS-negative primaries, 50 per cent (2/4) had TS-positive nodes and 50 per cent (2/4) had TS-negative nodes [kappa = -0.0131, 95 per cent confidence interval: (-0.2958, 0.2696), P = 0.9274]. Two of the three TS-negative primaries that had metastasized to regional lymph nodes were associated with TS-positive lymph nodes. Our findings indicate that expression of TS by a primary CRC does not correlate with nodal metastases or nodal TS expression. Nodal expression of TS may be important in predicting response to 5-fluorouracil when a primary CRC is TS-negative.