758 - Feasibility of Oral Administration of S-1 for Adjuvant Chemotherapy of Gastric Cancer; 4-week S-1 Administration followed by 2-week rest vs. 2-week Administration followed by 1-Week Rest

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ABSTRACT Background In 2006, ACTS-GC study revealed that S-1 is an effective adjuvant therapy of gastric cancer. Following the study, S-1 is used as the standard treatment for adjuvant therapy for gastric cancer in Japan. S-1 therapy with 4-week administration followed by 2-week rest was continued for 6 months in 78%, and 12 months in 66% of the patients. The compliance is the critical problems of the therapy. Tukuda et al. reported a randomized study of S-1 for adjuvant chemotherapy of advanced head and neck cancer, showing that the feasibility of 4-week administration followed by 2-week rest for 6 months was 29%, and 2-week administration followed by 1-week rest was 40%. They claimed that the 2-week administration followed by 1-week rest seems to be more feasible in adjuvant therapy of squamous cell carcinoma of the head and neck. There is no study of the feasibility for S-1 in adjuvant chemotherapy of gastric cancer. Here we conducted a study to evaluate the feasibility, safety and efficacy of S-1 in adjuvant chemotherapy of gastric cancer. Method The criteria for eligibility were histologically proven gastric cancer of stage II (excluding T1), IIIA or B with D2 lymph-node dissection. Patients were randomly assigned to either arm A; S-1 administration for 4 weeks followed by a 2-week rest or arm B; S-1 administration for 2 weeks followed by a 1-week rest. In each arm, the therapy was continued for 12 months unless there was any recurrence or severe adverse event. The primary end point was feasibility. The secondary were the safety of S-1, relapse-free and overall survival. Results We randomly assigned 46 patients to the arm A or B between May 2008 and February 2010. The first interim analysis showed the feasibility of the arm A and B, those were 83% and 100% in 6 months, 49% and 89% in 12 months respectively. S-1 administration for 2 weeks followed by a 1-week rest was more feasible in adjuvant chemotherapy of gastric cancer (P = 0.0046). Adverse events of grade 3 in the arm A were anorexia (8.0%), nausea (4.0%). There is no event of grade 3 in the arm B, and no event of grade 4 in both arms. Efficacy of the therapies; relapse-free survival and overall survival will be reported in the few years. Conclusion The schedule of 2-week administration followed by 1-week rest is more feasible for oral administration of S-1 in adjuvant chemotherapy of gastric cancer. Disclosure All authors have declared no conflicts of interest.