Randomized controlled phase II study of alternate-day S-1 as adjuvant chemotherapy for gastric cancer.

Abstract

114 Background: Based on the results of ACTS-GC, oral administration of S-1 for 1 year is considered standard postoperative adjuvant chemotherapy for gastric cancer in Japan. However, the 1-year treatment completion rate was only 65.8%, and completion of the treatment is a problem to be solved. On the other hand, we experienced in clinical practice that the alternate-day administration of S-1 reduced adverse effects and was tolerable for advanced gastric cancer patients unwilling to continue the standard daily administration. We therefore conducted a multi-center cooperative prospective study to compare daily with alternate-day administration of S-1 as postoperative adjuvant therapy for gastric cancer. Methods: Patients with Stage II or III gastric cancer who underwent curative surgery were randomly assigned to receive standard daily administration (group A: S-1 80-120 mg/day according to BSA, days 1 to 28, every 6weeks, for 1 year) or alternate-day administration of S-1 (group B: S-1 80-120 mg/day according to BSA, every other day, for 15 months). The primary endpoints were treatment completion rate and relative dose intensity. Secondary endpoints were safety, overall survival, and relapse-free survival. Results: A total of 73 patients were enrolled. As of August 30, 2011 analysis of the compliance data of 62 cases had been completed. The results showed a treatment completion rate of 74.2% in group A and 93.5% in group B and relative dose intensity of 72.1% in group A and 85.6% in group B, and compliance tended to be better in group B. Assessment of survival time showed a median follow-up time of 545 days, a 1-year survival rate of 93.8% in group A and 96.9% in group B and 1-year relapse-free survival rate of 79.5% in group A and 90.7% in group B. Digestive system adverse events were less frequent in group B than in group A. Conclusions: We will report the data from the final analysis at this meeting. The current data show improved compliance and mitigation of adverse effects with alternate-day administration of S-1, and it appears to be a more sustainable option for adjuvant chemotherapy for Stage II and III gastric cancer.