Regional differences in patient (pt) characteristics of AVAGAST: An exploratory comparison in chemotherapy plus placebo (PL) arm between Japanese (JPN) and the rest of the world (ROW) pts.

Abstract

100 Background: AVAGAST study showed regional differences in efficacy, including notable differences in progression free survival (PFS) and overall survival in the PL arm. In Japan, there is a certain number of pts with minimal peritoneal metastasis (PM) diagnosed only by laparoscopy or open surgery, which seems unusual in Western as well as in other Asian countries, and it might have led the differences. Therefore, an exploratory analysis was conducted among the PL arm to examine pt characteristics including PM associated with differences in outcome between JPN and ROW. Methods: We compared PFS of PL arm between pts enrolled from JPN and those from ROW. Hazard ratio (HR) and its 95% confidence interval (95%CI) between JPN and ROW were calculated using Cox’s proportional hazard model for each major covariates (disease status, performance status, prior gastrectomy, prior (neo)adjuvant chemotherapy, age, sex, primary site, liver metastasis (mets), number of metastatic sites, disease measurability, histologic type, maximum of tumor size, sum of tumor size, bone mets, PM and only PM) Results: 188 pts from 14 sites were enrolled from JPN, of which 94 pts were randomized to PL arm. Compared with 293 pts from ROW in PL arm, PFS tend to be favorable in JPN. Subgroups of JPN without liver mets, with diffuse or mixed type gastric cancer (GC), with PM and with only PM were clearly favorable than that of ROW. The difference in subgroup with PM was especially large with lower confidence limit of 1.21. When the pts with only PM were excluded, the difference of PFS in PL arm between JPN and ROW became smaller ( Table ). Conclusions: In this exploratory analysis, pts with PM in JPN had a better prognosis than ROW pts. Understanding this unique pt population may provide insight to the regional differences in outcome noted on this study. [Table: see text]