794PGastrectomy plus chemotherapy versus chemotherapy alone for advanced gastric cancer with a single non-curable factor: Exploratory analysis in the patients who were enrolled in JCOG0705/KGCA01 phase III trial (REGATTA) and could continue chemotherapy

Background REGATTA is a phase III trial to compare chemotherapy alone (arm A) and reduction surgery followed by chemotherapy (arm B) for advanced gastric cancer with a single non-curable factor. The trial failed to show superiority of reduction surgery, which could be partially explained by poor compliance of chemotherapy in arm B. This exploratory analysis aims to clarify whether upfront surgery has survival benefit in patients (pts) who could continue chemotherapy for some period, enrolled in REGATTA. Methods In REGATTA, 175 pts were assigned to arm A (86 pts) and arm B (89 pts). S-1 80 mg/m2 for 3 weeks and CDDP 60 mg/m2 on day 8 was repeated every 6 weeks. The pts were limited to those for whom chemotherapy was continued at 2, 4, or 6 months after randomization (cohort-2M, cohort-4M, or cohort-6M, respectively) and pts who underwent gastrectomy in arm A were excluded. The overall survival (OS) was defined as the duration from the date at 2, 4, or 6 months after randomization to the date of the death from any cause or to the last date of contact for a surviving pt. Results Examined pts were 130 (59 in arm A and 71 in arm B) in cohort-2M, 111 (50 in arm A and 61 in arm B) in cohort-4M, and 90 (43 in arm A and 47 in arm B) in cohort-6M, respectively. In cohort-2M, the median survival time (MST) was 14.1 months (m) (95% CI, 11.7-16.6) in arm A and 12.6 m (9.9-15.9) in arm B with hazard ratio (HR) of 0.935 (0.641-1.635). The OS was 9.7% (3.2-20.5) in arm A and 17.9% (9.2-28.8) in arm B at 3-year. In cohort-4M, the MST was 13.1 m (10.3-18.8) in arm A and 11.5 m (8.4-15.1) in arm B with HR of 0.954 (0.629-1.448). The OS was 11.5% (3.8-24.0) in arm A and 21.2% (11.0-33.6) in arm B at 3-year. In cohort-6M, the MST was 13.8 m (9.8-22.1) in arm A and 10.9 m (6.6-16.6) in arm B with HR of 0.860 (0.535-1.383). The OS was 13.2% (4.3-27.0) in arm A and 26.0% (13.1-41.0) in arm B at 3-year. Conclusions Among pts having certain period of chemotherapy, there seem to be more long survivors in arm B than the arm A. Reduction surgery may still be promising if chemotherapy compliance after surgery could be improved. Clinical trial identification UMI01012, Feb 2008. Legal entity responsible for the study Japan Clinical Oncology Group (JCOG). Funding The Ministry of Health, Labour and Welfare of Japan and the Korean Gastric Cancer Association. Disclosure All authors have declared no conflicts of interest.