Introduction
Although gastric cancer is one of the most common causes of cancer death in the world, the burden of gastric cancer in the United States tends to be underestimated relative to that of other cancers of the digestive system. In fact, the 5-year survival rate from gastric cancer remains poor (~32%)1 in the United States, and this is largely because gastric cancers are not diagnosed at an early stage when curative therapeutic options are available. Cumulative epidemiologic data consistently demonstrate that the incidence of gastric cancer in the United States varies according to ethnicity, immigrant status, and country of origin. It is important for practicing gastroenterologists in the United States to recognize individual risk profiles and identify people at higher risk for gastric cancer. Hereditary diffuse gastric cancer is an inherited form of diffuse-type gastric cancer and has pathogenic variants in the E-cadherin gene that are inherited in an autosomal dominant pattern. The lifetime risk of gastric cancer in individuals with HDGC is very high, and prophylactic total gastrectomy is usually advised. This article focuses on intestinal type cancer.
Epidemiology
Gastric cancer (proximal and distal gastric cancer combined) is the fifth most frequently diagnosed cancer and the third most common cause of cancer death worldwide, with 1,033,701 new cases and 782,685 deaths in 2018.2 Gastric cancer is subcategorized based on location (proximal [i.e., esophagogastric junctional, gastric cardia] and distal) and histology (intestinal and diffuse type), and each subtype is considered to have a distinct pathogenesis. Distal intestinal type gastric cancer is most commonly encountered in clinical practice. In this article, gastric cancer will signify distal intestinal type gastric cancer unless it is otherwise noted. In general, incidence rates are about twofold higher in men than in women. There is marked geographic variation in incidence rates, and the age-standardized incidence rates in eastern Asia (32.1 and 13.2, per 100,000) are approximately six times higher than those in northern America (5.6 and 2.8, per 100,000) in both men and women, respectively.2 Recent studies evaluating global trends in the incidence and mortality of gastric cancer have demonstrated decreases worldwide.3-5 However, the degree of decrease in the incidence and mortality of gastric cancer varies substantially across geographic regions, reflecting the heterogeneous distribution of risk profiles. A comprehensive analysis of a U.S. population registry demonstrated a linear decrease in the incidence of gastric cancer in the United States (0.94% decrease per year between 2001 and 2015),6 though the annual percent change in the gastric cancer mortality in the United States was lower (around 2% decrease per year between 1980 and 2011) than in other countries.3Several population-based studies conducted in the United States have demonstrated that the incidence of gastric cancer varied by ethnicity, immigrant status, and country of origin, and the highest incidence was observed among Asian immigrants.7,8 A comprehensive meta-analysis examining the risk of gastric cancer in immigrants from high-incidence regions to low-incidence regions found a persistently higher risk of gastric cancer and related mortality among immigrants.9 These results indicate that there are important risk factors such as environmental and dietary factors in addition to the traditionally considered risk factors including male gender, age, family history, and tobacco use. A survey conducted in an ethnically and culturally diverse U.S. city showed that gastroenterology providers demonstrated knowledge deficiencies in identifying and managing patients with increased risk of gastric cancer.10 Recognizing individualized risk profiles in higher-risk groups (e.g., immigrants from higher-incidence/prevalence regions) is important for optimizing management of gastric cancer in the United States.
