Better efficacy of S-1 treatment for thymic carcinoma: case report and review of the literature

Abstract

Primary thymic carcinoma is a rare tumor of the thymus gland. The role of chemotherapy in treating advanced thymic carcinoma is unclear. It has recently been reported that thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), and orotate phosphoribosyltransferase (OPRT) expression may be important factors when predicting the effectiveness of 5-fluorouracil-based chemotherapy (Kaira et al., 74:419–425, 2011). In this report, we describe three cases in which S-1 or S-1 combination treatment was given as second-line therapy for thymic carcinoma, and examine the relationships between the immunohistochemical expression of TS, DPD, and OPRT and treatment effectiveness. There were no deaths due to toxicity. Two patients achieved partial remission (PR), and one patient achieved stable disease (SD). These results suggest that S-1 is a safe and promising regimen for thymic carcinoma. Immunohistochemical staining for OPRT expression tended to be stronger in the two PR cases than in the SD case. Based on the present results, it appears that S-1 may be useful for treating unresectable thymic carcinoma, and that OPRT expression may predict the response to S-1 treatment. Further clinical studies are needed to confirm these findings.