Despite the worldwide decrease in gastric cancer incidence and mortality over the past 5 decades, it is still the third-leading cause of cancer-related death. Understanding the epidemiology and
risk factors for gastric cancer can aide in determination of risk, screening, and prevention. In the March issue of Clinical Gastroenterology and Hepatology, Aaron P. Thrift and Hashem B. El-Serag review the epidemiology
of gastric cancer along with screening and prevention efforts to reduce global morbidity and mortality.
The authors explain that gastric cancer was the leading cause of cancer deaths worldwide until the 1980s, when the incidence of lung cancer began to increase and the incidence of gastric cancer
began to decrease. Since then, there has been a steady decrease in gastric cancer incidence and mortality in developed nations (such as North America, Northern Europe, and Australia), and delayed
but similar decreases in areas with high incidence rates of gastric cancer (such as Japan, and Korea (see Figure). Nonetheless, fatality rates of gastric cancer remain at 75% worldwide.
The highest incidence rates
for gastric cancer in men and women were observed in Eastern Asia, Central and Eastern Europe, and South America. In 2018, the lowest incidence rates for gastric cancer were in
North America and African regions.
Thrift and El-Serag describe the 2 main subsites of gastric cancer: cardia gastric cancer (arising in the area of the stomach adjoining the esophagogastric junction) and noncardia gastric cancer
(arising from more distal regions of the stomach).
The authors state that although the effectiveness of treatment has increased, in the United States, overall 5-year rates of survival for patients with a diagnosis of gastric cancer is among the
lowest for all cancers. The prognosis for patients with gastric cancer is related to stage at diagnosis. Although the proportion of unstaged cases decreased from 2001 through 2015, the proportion of gastric cancer cases that had localized, regional, or distant-stage disease remained stable over time. Surprisingly, 35% of patients with gastric
cancer in the United States are diagnosed with distant-stage disease. Thrift and El-Serag studied trends in 5-year relative age-adjusted gastric cancer survival by stage and found that 5-year survival rates have been increasing since 2000.
In the United States, gastric cancer is diagnosed most frequently among people 65 to 74 years old—the average age at diagnosis is 69 years. The authors review geographic differences in overall
gastric cancer incidence rates and trends over time. For example, in the United States number of states with age-standardized incidence rates for
gastric cancer greater than 8 per 100,000 persons decreased from 7 states (Hawaii, New York, New Jersey, Rhode Island, Connecticut, California, and Louisiana) in 2003 to 3 states (Alaska, New
York, and Hawaii) by 2015. The articles provides a summary table of findings from epidemiology studies of gastric cancer in the United States.
What are the risk factors for gastric cancer? Chronic infection with Helicobacter pylori is the main
cause of gastric cancer, accounting for approximately 89% of distal gastric cancer cases worldwide. The International Agency for Research on Cancer confirmed H pylori as a class I
carcinogen in 2009.
The prevalence of H pylori infection is higher in Central and South America and in parts of Asia and Eastern Europe than in North America, Australia, or Western Europe. As many as 10% of
gastric cancers can be attributed to less-common causes, such as infection with the Epstein–Barr virus, autoimmune gastritis, or Ménétrier disease. Other factors associated with an increased risk for
gastric cardia and noncardia cancers include smoking tobacco, low socioeconomic status, low level of physical activity, and radiation exposure. Obesity and gastroesophageal reflux disease are
associated only with an increased risk of gastric cardia cancer.
As for food, nonstarchy vegetables and fruits have been proposed to protect against gastric cancer, whereas a high-salt diet has been associated with a higher risk for gastric cancer. Salt might
have a synergistic effect with H pylori infection to further increase for gastric cancer.
Thrift and El-Serag write that in 2019, an estimated 27,510 adult Americans will receive a diagnosis of gastric cancer, and 11,140 will die from gastric cancer. Gastric cancer prevention
has focused on screening and surveillance as well as H pylori screening and eradication. In geographic regions with a high gastric cancer burden, population-based H
pylori serology screening is cost effective, particularly if performed in persons younger than age 50 years. However, in countries with a low incidence of gastric cancer, including the
United States, such a screening strategy is thought to be too costly and generally unwarranted. The authors conclude that population-based programs of screening
and treatment for H pylori hold the greatest promise for reducing the burden of gastric cancer.