4111 Background: The Wnt/β-catenin signaling pathwaycontrols cell proliferation and differentiation. Disruption of this pathway has been shown in the majority of colorectal (CRC) and gastric cancer (GC). The TCF7L2 complex plays a critical role in this pathway. Interaction of TCF7L2 and β-catenin results in translocation to the nucleus and leads to up-regulation of target genes, including c-myc and cyclin D1. Previous reports have shown that TCF7L2 polymorphism rs7903146 C/T is associated with CRC risk and outcome; however, the prognostic role of this polymorphism in GC is unknown. Therefore, we tested the hypothesis of whether this polymorphism could predict outcome in GC in three independent cohorts. Methods: A total of 369 patients (pts) with histopathologically-confirmed localized GC were enrolled from Japan (n=169), the US (n=137), and Austria (n=63) between 2002 and 2010. Results: In the US cohort, pts with at least one-T allele ((T/T or C/T; n=46) showed a median TTR of 1.7 yrs vs. 4.4 yrs compared to pts homozygous C/C (n=76) (HR: 2.09 95%CI: 1.21- 3.59, p=0.0053). A similar trend was shown in the Austrian cohort, where pts harboring at least one-T allele (n=25) showed a median DFS of 2.08 yrs vs. 5.42 yrs for pts homozygous C/C (n=38) (HR: 1.79 [95%CI: 0.90-3.55], p=0.092). Moreover, in the Japanese cohort, pts homozygous for T/T demonstrated (n=2) a median DFS of 0.15 yrs vs. 4.82 yrs for pts harboring at least one-C allele (n=165) (HR: 10.5 [95%CI: 2.46-45.5], p=0.001). These results were confirmed in the OS in the US and Japanese cohorts. Pts at least one-T allele (n=46) showed a median OS of 3.3 yrs vs. 5.5 yrs for pts homozygous C/C (n=76) (HR: 2.41 95%CI: 1.28-4.53, p=0.0043) in the US cohort, while pts homozygous T/T showed (n=2) a median OS of 0.22 yrs vs 5.76 yrs for pts harboring at least one-C allele (n=165) (HR: 15.2 [95%CI: 3.50-66.7], p<0.001). Conclusions: TCF7L2 polymorphism was associated with worse prognosis in recurrence in pts with GC in three independently global cohorts. This polymorphism may be negative prognostic factor in GC regardless of ethnicity and etiology, suggesting the importance role of Wnt/β-Catenin signaling in GC.