18122 Background: Docetaxel is active against chemotherapy-pretreated non-small-cell lung cancer (NSCLC). S-1 is a novel oral fluoropyrimidine, composed of tegafur, 5-chloro-2,4-dihydroxypyridine (dihydropyrimidinedehydrogenase inhibitor), and potassium oxonate (orotate phosphoribosyl transferase inhibitor). It has been commercially available and used for NSCLC in Japan. We conducted this study to evaluate the efficacy and safety of docetaxel combined with S-1 in NSCLC patients (pts) who were previously treated with one or more regimens. Methods: Eligible pts were required to have histologically or cytologically confirmed measurable or evaluable stage IIIB or IV NSCLC, age= 20 years, one or more previous chemotherapy, a performance status (PS) 0–1, and adequate organ function and bone marrow reserve. In this study, pts received S-1 (80 mg/m2 orally on days 1–14) and docetaxel (40mg/m2 IV on days 1). Treatment was repeated every 3 weeks. Results: Between January 2005 and May 2006, 30 pts were enrolled on this study. 29 pts were eligible and evaluable. Median age was 67 (48–79), male/female (23/6), PS 0/1 (9/20), stage IIIB/IV (7/22), and prior chemotherapy regimen 1/2/3 (23/4/2). 28 pts received a platinum-based chemotherapy. Response: PR=7(24%), SD=13, PD=7, NE=2. Median survival time was 10.2 months. Grade 3/4 toxicities (% of pts) were as follows: leukocytes 6/0 (20.6%), neutrophils 7/3 (34.4%), platelets 0/0, infection 0/1 (3.4%), fever 2/0 (6.9%), diarrhea 1/0 (3.4%), neurology 0/1 (3.4%), and mucositis 1/0 (3.4%). There were no treatment-related deaths. Conclusions: The combination of docetaxel and S-1 was effective with acceptable toxicity in pts with previously treated NSCLC. These results warrant further investigations of this regimen a randomized controlled trial as a second-line treatment for NSCLC. No significant financial relationships to disclose.