Geographical differences in risk factors, systems and outcomes in gastric cancer

Gastric cancer is one of the leading causes of malignancy-related death worldwide; however, a unique demographic distribution exists. Global differences are seen with an increased incidence noted in Asia as compared to Western countries. Demographic and pathologic patterns also differ widely between Asian and Western patients. It is apparent that distal tumors of a favorable histologic subtype are more common in Asian patients, with a tendency towards a mixed or diffuse histology. Western patients, on the contrary, tend to have more advanced disease with more proximal tumors. It still remains unclear what the exact etiology is behind this demographic difference. The role of Helicobacter pylori, in addition to other etiologies, perhaps diet-related or genetic, may also contribute to the disparities seen. Treatment strategies also demonstrate geographic differences, with Western countries often favoring a neoadjuvant chemotherapy approach, prior to surgical resection. Surgical resection remains the mainstay of therapy for gastric cancer in Asian countries, with an emphasis on the extent of lymphadenectomy. Often, lymph node dissection and examination occur intraoperatively, according to the Japanese classification system. This is unlike the Western technique that tends towards en bloc submission of the gastric specimen with the lymphadenectomy to pathology for examination. Although much debate has historically centered on the extent of lymphadenectomy, D2 lymphadenectomy is now widely considered standard for resection for gastric cancer. Despite the American Joint Committee on Cancer (AJCC) staging system being widely referenced, Asian countries demonstrate an improved survival, even when matched stage for stage with patients in Western countries. Demographic factors, prevalence of obesity, location of tumor, and other contributing factors may impact the differences seen in outcome. This review focuses on the etiologies, treatment, national systems, and outcomes of gastric cancer, particularly as it relates to global differences seen in the approach to treating gastric cancer.