Background: S-1, a novel oral fluoropyrimidine, has potent antitumor activity against non-small-cell lung cancer (NSCLC). Meanwhile, leucovorin enhances the efficacy of 5-fluorouracil by inhibiting thymidylate synthase. Therefore, this phase II clinical trial evaluated the safety and efficacy of S-1 plus leucovorin combination therapy for previously treated patients with NSCLC. Patients and methods: Patients with stage IIIB or IV NSCLC were prospectively enrolled if they received 1 or 2 prior chemotherapy regimens. S-1 (40-60. mg) and leucovorin (25. mg) were administered together orally twice per day for 7 consecutive days followed by 7 days of rest. This 2-week cycle was repeated for a maximum of 25 cycles until the onset of disease progression or unacceptable adverse events. Endpoints included objective tumor response, progression-free survival, overall survival, and safety. Results: Among 33 patients, 6 (18.2%), 14 (42.4%), and 11 (33.3%) had partial response, stable disease, and progressive disease, respectively. Median progression-free and overall survival times were 3.5 and 11.7 months, respectively. The common grade 3 toxicities included stomatitis (18.2%), anorexia (12.1%), and neutropenia (9.1%). One patient had pneumatosis cystoides intestinalis, and another experienced paralytic ileus. There were no treatment-related deaths. Conclusions: S-1 plus leucovorin combination therapy demonstrated promising efficacy and an acceptable toxicity profile in previously treated patients with NSCLC.
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