Differences in the efficacy of S-1 monotherapy according to histological type in pretreated patients with advanced non-small cell lung cancer

Background S-1 is a novel antimetabolic agent that inhibits thymidylate synthase. The expression of thymidylate synthase is higher in squamous (Sq) non-small cell lung cancer (NSCLC) than in non-Sq NSCLC. The aim of this retrospective study was to assess the efficacy of S-1 monotherapy for advanced NSCLC according to the histological subtype. Methods We reviewed the clinical records of patients with advanced NSCLC treated with S-1 monotherapy as second- or third-line therapy between May 2005 and July 2012 at the Shizuoka Cancer Center. Results A total of 71 patients were included in this retrospective study. Patient characteristics were similar in the Sq NSCLC (n = 15) and non-Sq NSCLC (n = 56) groups, except with regard to gender and smoking status. The overall response rates were 0% (95% confidence interval [CI] 0–17%) for Sq NSCLC and 11% (95% CI 3–19%) for non-Sq NSCLC (P = 0.33). For Sq NSCLC and non-Sq NSCLC, the median progression-free survival times were 2.1 and 2.8 months (P = 0.02), respectively, and the median overall survival times were 6.1 and 10.1 months (P = 0.01), respectively. Conclusion S-1 monotherapy may be more effective in patients with non-Sq NSCLC than in those with Sq NSCLC.