Predictive value of immunohistochemical thymidylate synthase expression for histological response to Tegafur/Uracil (UFT) in oral squamous cell carcinoma.

Thymidylate synthase (TS), an enzyme involved in the DNA synthesis, is a critical target for fluoropyrimidines. We investigated the relationship between the level of tumoural TS expression and response to tegafur/uracil (UFT) in 26 patients with oral squamous cell carcinoma. The patients received peroral administration of UFT alone preoperatively. In biopsy specimens, TS expression level was assessed by the immunohistochemical staining and graded as 1+, 2+ or 3+ according to the frequency of strongly-stained tumour cells. Out of 26 tumours, 10 (38.5%), 10 (38.5%) and 6 (23.1%) cases were categorized as 1+, 2+ and 3+, respectively. The response to UFT was histologically evaluated by a grading system according to the extent of degenerative or necrotic cancer cells in surgical specimens. Results showed patients with the lower TS expression had the higher response and there was a statistically significant association between TS expression and response to UFT (P=0.031). This finding suggests that TS expression is a predictor of chemosensitivity to UFT in oral squamous cell carcinomas.