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Dr Vũ Quốc Duy

The epidemiology of gastric cancer is changing in the United States, say researchers. Incidence rates of noncardia gastric cancer are rising among individuals younger than 50 years, although it’s falling in older patients. Women will soon be more at risk than men.

The findings were published online January 19 in the Journal of the National Cancer Institute.

The data show “a new pattern in gastric cancer epidemiology,” Martin Blaser, MD, and Yu Chen, MD, New York University School of Medicine in New York City, write in an accompanying editorial.

“This pattern appears to identify a new form of noncardia stomach cancer,” they add.

The rising incidence of noncardia gastric cancers in individuals younger than 50 that is reported in the current study — together with the fact that the largest increase in noncardia gastric cancer involves tumors in the gastric corpus and that women are more at risk of developing corpus cancer than men — suggests that a new type of gastric cancer is taking hold in the United States, defined by the editorialists as “CYF” cancers — corpus-dominant, young age–dominant, female-dominant gastric cancers.

“Gastric cancer has always been more common in men, but these data in women predict an unprecedented reversal,” Dr Blaser and Dr Chen write.

Driven by Infection or Autoimmunity?
“The initial step for noncardia gastric carcinogenesis is atrophic gastritis, driven by either Helicobacter pylori infection or autoimmunity,” note the study authors, led by William Anderson, MD, MPH, National Cancer Institute, Bethesda, Maryland.

However, in recent years, the prevalence of H pylori has declined significantly, not only in the United States but also globally, they note. At the same time, the prevalence of autoimmunity has increased as Western lifestyles change.

These two trends prompted investigators to see whether there has been a shift in the incidence of gastric cancer as well as in the type of gastric cancer manifested in the US population across almost 2 decades.

To track the incidence of gastric cancer, they mined data from 1995 to 2013 in the National Cancer Institute’s Surveillance, Epidemiology, and End Results database and in 45 North American Association of Central Cancer Tumor Registries (NAACCR).

These data represent about 80% of the US population.

“There were 137,447 noncardia cancers in 4.4 billion person-years of observation,” the investigators report.

The majority of the adenocarcinomas recorded in the NAACCR database were found in non-Hispanic whites; people aged 50 years or older at the time of diagnosis; and in counties were rates of poverty were less than 20%, they add.

However, incidence rates varied considerably, depending on ethnicity.

For example, age-standardized rates (ASRs) of noncardia gastric cancer were 2.2 per 100,000 person-years among non-Hispanic whites; 6.2 per 100,000 person-years for non-Hispanic blacks; and 7.7 per 100,000 person-year for non-Hispanic others, primarily Asians.

The sites involved in these cancers — and their incidence rates over the years — also varied considerably, depending on sex and age.

Confining their analysis to non-Hispanic whites — the only race in which significant changes in the epidemiology of noncardia cancer were seen — “12.8% of noncardia cancers were localized to the gastric fundus, 19.8% to the corpus, 35.0% to the antrum, and 5.5% to the pylorus,” the study authors report.

Regarding the estimated annual percentage change (EAPC) in the incidence of these cancers, the researchers found that overall, the incidence for noncardia cancer dropped by 3% per year (95% confidence interval [CI] = -3.3% to -2.7%) between 1995 and 2013.

Dr Vũ Quốc Duy

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