Clinicopathologic study of S-1 alone in elderly patients with oral squamous cell carcinoma

Abstract

S-1 is an anticancer agent comprising tegafur as a 5-FU prodrug, gimeracil, and oteracil potassium. It has been suggested that the effectiveness of S-1 depends on the expression of enzymes stimulating fluoropyrimidine anticancer agents, such as thymidylate synthase （TS）, dihydropyrimidinede hydrogenase （DPD）, and orotate phosphoribosyl transferase （OPRT）. The goal of this study was to investigate the regimen, dosage, and correlation between the response and adverse events to S-1 and the expression of TS, DPD, and OPRT in elderly patients with oral squamous cell carcinoma. Three CR cases, one PR case, and three SD instances were reactions to S-1. The final dosing schedule in 5 patients was a 2-week administration period followed by a 1-week break; the dose was 67-80％ of the recommended amount in 5 patients, and 6 patients had some adverse event. The low expression of TS enzyme in cytoplasm was associated with the effect of S-1. Low dosage of S-1 with 2-week administration followed by 1-week rest was efficient and safe for the elderly patients with oral squamous cell carcinoma. In addition, it was suggested that TS expression in the cytoplasm might be helpful in the selection of S-1 therapy using immunohistochemistry.