Nature Versus Nurture: The Impact of Nativity and Site of Treatment on Survival for Gastric Cancer

Abstract

Purpose: The prognosis of gastric cancer patients is substantially better in Asia than in the West. Genetic, environmental, and treatment factors have all been implicated. We sought to explore the extent to which the place of birth and the place of treatment influences survival outcomes in Korean and US patients with localized gastric cancer. Patients and Methods: Patients with localized gastric adenocarcinoma undergoing potentially curative gastrectomy from 1989 – 2010 were identified from the Surveillance, Epidemiology, and End Results (SEER) registry and from two single-institution databases from the US and Korea. Patients were categorized into three groups: KK (Koreans born and treated in Korea), KUS (Koreans born in Korea but treated in the US), and W (white Americans born and treated in the US), and overall survival rates were compared. Results: The final cohort consisted of 16,622 patients: 3,984 (24.0%) KK, 1,046 (6.3%) KUS, and 11,592 (69.7%) W patients. KK patients had longer unadjusted median and 5-year overall survival rates (100.6 months, 72.5%) than KUS (52 months, 47.2%) and W (18 months, 16.4%; p<0.001 for all comparisons) patients. This finding persisted on subset analyses of stage IA patients, patients without cardia/GEJ tumors, patients with >fifteen examined lymph nodes, and patients treated at a US center of excellence. On multivariable analysis, KUS (HR 1.98, 95% CI 1.54-2.55, p<0.001) and W (HR 5.01, 95% CI 4.15-6.06, p<0.001) patients had an increased risk of mortality when compared to KK patients. Conclusions: Both the place of birth and the place of treatment significantly contribute to the improved prognosis of patients with gastric cancer in Korea relative to those in the US, implicating both nature and nurture in this phenomenon.