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Impact of Korean Ethnicity and Site of Treatment on Outcomes of Patients With Resectable Gastric Cancer
Danbee H. Kim*1,2, Christy E. Cauley1, David C. Chang1, Kyo Young Song2, John T. Mullen1
1Surgery, Massachusetts General Hospital, Newton, MA; 2Surgery, Seoul St. Mary's Hospital, Seoul, Korea (the Republic of)
Introduction: It is well known that the prognosis of Korean patients with gastric cancer is much better than that of Caucasian patients. Several prior studies have explored potential factors to explain this survival difference, yet few studies have simultaneously examined the role of ethnicity and the site of treatment on overall survival. In this study, we sought to evaluate the impact of ethnicity and the site of treatment on overall survival in four distinct cohorts of patients from South Korea and the United States.
Methods: We identified 4,256 Korean patients from a Korean center of excellence (COE), 1,345 Korean and 23,979 non-Koreans patients from the Surveillance, Epidemiology, and End Results cancer registry, and 380 patients from a US COE who underwent gastrectomy for gastric adenocarcinoma between 1998 and 2010. Patients with gastroesophageal junction tumors were excluded. Clinicopathologic characteristics, operative details, and oncologic outcomes were collected. Patients were stratified according to ethnicity and site of treatment: Koreans treated at a COE in Korea[PHS IS1], Korean immigrants treated in the US (SEER), non-Koreans treated in the US (SEER), and patients treated at a COE in the US. Cox logistic regression analysis was performed to identify predictors of overall survival.
Results: Koreans treated in a Korean COE were younger, had more distal intestinal type adenocarcinomas, had earlier stage disease, and were more likely to undergo a partial gastrectomy and an adequate lymph node sampling (ALNS, defined as >/= 15 examined lymph nodes) than all cohorts treated in the US. Although Korean-born patients treated in the US showed many similar characteristics, there were fewer males, more intermediate-type and node-positive cancers, and a lower likelihood of ALNS. Patients treated at a US COE had more proximal, poorly cohesive-type cancers, more advanced stages of disease, and were more likely to receive either a total gastrectomy or an esophagogastrectomy. Patients treated at a Korean COE had a significantly higher rate of ALNS (97%) than patients treated at either a US COE (66%) or at a SEER hospital (45% for Korean immigrants and 35% for non-Koreans). Compared to Korean patients treated at a Korean COE, non-Korean patients treated in the US at a SEER hospital had a significantly worse overall survival (Hazard ratio [HR] = 4.25), as did patients treated at a US COE (HR = 2.86) and Korean immigrants treated in the US at a SEER hospital (HR = 1.98).
Conclusion: Korean ethnicity confers a distinct survival advantage in patients with gastric cancer, but the site of treatment is an equally important variable. Treatment factors, such as the extent of surgery and the use of adjuvant therapies, deserve more attention as an explanation for observed disparities in gastric cancer outcomes.
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