393 Background: S-1 is an oral anticancer agent combining tegafur, a prodrug of 5-fluorouracil (5-FU), with 5-chloro-2,4-dihydroxypyridine and potassium oxonate. S-1 has shown efficacy for cytokine and/or tyrosine-kinase inhibitor (TKI) refractory metastatic renal-cell carcinoma (mRCC). We report the final results of a phase II study and evaluate 5-FU-related enzymes as a predictor of the response to S-1. Methods: 45 patients received S-1 at a dose of 40 mg/m2 twice daily for 28 days, followed by 14 days of rest. The primary endpoint was the objective response rate (ORR). The secondary endpoints of progression-free survival (PFS) and overall survival (OS) were estimated by the Kaplan-Meier method. Formalin-fixed, paraffin-embedded specimens obtained by radical nephrectomy were used for mRNA expression assay, performed by reverse-transcriptase polymerase chain reaction. Results: 45 patients including 6 were progressed after TKI were enrolled from April 2006. 24 patients received more than 5 cycles, and 2 continued to receive S-1 as of October 2011. Two (4.4%) of the 45 patients had complete responses to S-1, 9 (20.0%) had partial responses, and 28 (62.8%) had stable disease. The final PFS and OS were 9.2 and 42.8 months, respectively, and the PFS of TKI refractory patients was approximately two times of final PFS (18.0 months). The most common grade 3-4 adverse events according to CTCAE v.3.0 were similar to the previous report except for hemoglobin decreased and fatigue. On mRNA expression analysis, the expression level of thymidylate synthase correlated with ORR and PFS. On the other hand, OS did not differ significantly between patients with low expression and those with high expression of 5-FU-related enzymes. Conclusions: S-1 is effective and well tolerated in patients with cytokine and/or TKI refractory mRCC. Moreover, long-term treatment with S-1 is safe in mRCC patients enabling long-term disease control, especially in TKI refractory patients. Clinical trial with large number of TKI refractory patients is warranted to determine the efficacy of S-1.
Comparison of Tyrosine Kinase Inhibitor Versus Mammalian Target of Rapamycin Inhibitor as Second-line Molecular-targeted Therapy for Patients with Poor-risk Metastatic Renal Cell Carcinoma
