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Detailed study of stomach cancer incidence predicts changes in “typical” patient

Posted on January 19, 2018

A recent study found that the incidence of noncardia gastric cancers—those occurring in the antrum and pylorus—has been increasing for Americans under age 50.

In January 2018, a team of DCEG investigators published an updated analysis of U.S. cancer incidence in the lower part of the stomach—known as noncardia gastric cancer. Despite an overall downward trend at the population level, they showed a distinct split in rates across generations.

The researchers, led by M. Constanza Camargo, Ph.D., analyzed data from the North American Association of Central Cancer Tumor Registries, which includes 45 states and about 80% of the U.S. population, to track cancer trends by race/ethnicity, age, and birth year. In the general population, noncardia gastric cancer incidence fell by about 2.3% per year between 1995 and 2013. However, this seemingly favorable trend masks the 1.3% yearly increase in incidence among Americans younger than 50. Examining the data by birth year, Camargo and colleagues found that while people born before 1951 experienced decreasing rates of noncardia cancer over time, incidence went up over time among people in later generations. Earlier studies have shown a similar increase in incidence among young people but were not able to distinguish between Hispanic white and non-Hispanic white individuals due to lack of specificity in census data. In this analysis, trends were most pronounced in non-Hispanic whites, particularly women. The team also observed a modest increase in incidence among young Hispanic whites, and no significant increase among blacks or other races (mainly representing people of Asian descent).

Extrapolating these trends into the next few decades, the team predicted two major reversals in gastric noncardia cancer patterns in the U.S. population. First, around 2025, incidence rates are projected to become higher in women than in men, a reversal of the current sex ratio. Second, by 2030, overall incidence of noncardia cancer will no longer be decreasing. In coming decades, the medical community may need to re-envision the “typical” noncardia gastric cancer patient.

Additionally, the study authors question one of the leading explanations for changing noncardia cancer incidence in young people: an increase in Helicobacter pylori bacterial infections due to immigration from countries with higher infection rates. Instead, they suggest that the observed split between older and younger generations may be related to decreased bacterial exposure due to modern living conditions as well as the beginning of widespread antibiotic medication use in the 1950’s. They further explain that the stronger increase in incidence among women is consistent with the higher usage of antibiotics by women compared to men. The authors point to rising rates of autoimmune conditions in general and speculate that antibiotic medications may increase the risk of developing autoimmune gastritis, which is one of the major causes of noncardia gastric cancer. No matter the underlying cause of the trends, however, antibiotics remain a life-saving tool and should be used when medically necessary.

Reference: Anderson… Camargo et al. The changing face of noncardia gastric cancer incidence among US non-Hispanic whites. JNCI. January, 2018. DOI: https://doi.org/10.1093/jnci/djx262