Three-year outcomes of two phase II studies of adjuvant chemotherapy with S-1 plus oxaliplatin or capecitabine plus oxaliplatin in patients with stage III gastric cancer after D2 gastrectomy.

Abstract

94 Background: Two phase II trials of oxaliplatin-based adjuvant chemotherapy for patients (pts) with gastric cancer (GC) after D2 gastrectomy have been conducted in Japan; the J-CLASSIC study of capecitabine plus oxaliplatin (CAPOX) and the SOXaGC study of S-1 plus oxaliplatin (SOX). In the current study, we evaluated survival outcomes of the two trials. Methods: The J-CLASSIC, enrolling stage II and III pts from 12 centers between July 2012 and July 2013, evaluated eight cycles of CAPOX. The SOXaGC, enrolling stage III pts from 11 centers between July 2013 and February 2014, evaluated seven cycles of SOX after one cycle of S-1 monotherapy. The two studies were conducted sequentially and most centers (9 centers) participated in both trials. In this pooled analysis, we updated relapse-free survival (RFS) and overall survival (OS) information. The median follow-up time was 49 months in the J-CLASSIC and 39 months in the SOXaGC. Results: Fifty-nine stage III pts treated with CAPOX and 62 stage III pts treated with SOX were analyzed. The 3-year RFS and OS rates of SOX were 70.9% (57.8-80.5%) and 75.7% (63.0-84.6%), respectively, whereas the 3-year RFS and OS rates of CAPOX were 67.8% (54.3-78.1%) and 79.3% (66.5-87.7%), respectively. The hazard ratio (HR) of SOX in comparison to CAPOX was 0.925 (0.498-1.720) for RFS, suggesting the efficacy of the two treatments was similar. Trend of a different efficacy was observed in some particular subgroups; the HR for RFS was 1.732 (0.506-5.927) in the intestinal type and 0.735 (0.353-1.528) in the diffuse type, while that was 2.008 (0.447-9.016) in stage IIIA, 0.872 (0.266-2.857) in stage IIIB, and 0.597 (0.258-1.383) in stage IIIC. Conclusions: This is the first report of survival follow-up in Japanese GC pts with oxaliplatin-based adjuvant chemotherapy, which suggests comparable outcomes in both treatments for stage III GC. Different trend in the treatment effect by histologic type or stage warrants further evaluation in a larger cohort. Clinical trial information: UMIN000026883.