- A phase 3, open-label study examining 4 courses (6 months) vs 8 courses (1 year) of adjuvant S-1 in patients with stage 2 gastric cancer was stopped early when an interim analysis showed higher survival in the 8-course group.
Why this matters
- In an open-label, phase 3 trial (JCOG1104 [OPAS-1]), 528 patients were randomly assigned to 8 or 4 courses of postoperative S-1.
- Funding: Japan Agency for Medical Research and Development; Ministry of Health, Labour and Welfare of Japan; National Cancer Center Research and Development Fund, Japan.
- At interim analysis (50% enrollment), HR for relapse-free survival in the 8-course group was 2.52 (95% CI, 1.11-5.77), which exceeded the prespecified criteria for early termination of HR 1.37 (predictive probability for noninferiority at final analysis, 2.9%).
- OS at 3 years was 96.1% in the 8-course group and 92.6% in the 4-course group (HR, 3.37; 95% CI, 1.23-9.19).
- Early termination based on enrolled patients, rather than events.