Final Results of a Phase II Study of S-1 in Patients with Cytokine-refractory Metastatic Renal Cell Carcinoma

A planned primary analysis of a Phase II study of S-1 demonstrated that the drug was active and tolerable in Japanese patients with cytokine-refractory metastatic renal cell carcinoma. Furthermore, pharmacogenomic analysis suggested that low expression of thymidylate synthase mRNA may have been associated with clinical outcome in terms of overall response rate and progression-free survival. Here, we report the results of the final analysis assessing the efficacy and safety of S-1 including overall survival. Patients with renal cell carcinoma were eligible if they had had at least one regimen of cytokine for metastatic disease. S-1 was orally administered on Days 128 of a 42-day cycle until disease progression. The primary endpoint was the overall response rate, and the secondary endpoint included progression-free survival, overall survival and safety. A total of 45 patients were treated with S-1 and were fully assessable for efficacy and safety. At the final analysis, a response was seen in 11 patients (overall response rate, 24.4; 95 confidence interval: 12.939.5), including two patients who achieved a complete response. The final median progression-free and overall survival were 9.2 and 42.8 months, respectively. The safety profile of S-1 was favorable. It was suggested that there was no relation between overall survival and the expression level of thymidylate synthase. This final analysis confirms that S-1 treatment is effective and safe in patients with cytokine-refractory renal cell carcinoma.