The study, which was published January 19 by the Journal of the National Cancer Institute, found that the increase in the cancer — known as noncardia gastric cancer — was sharpest in non-Hispanic whites, especially women. Noncardia gastric cancer is defined as cancer of the lower part of the stomach. “Our key finding is that noncardia stomach cancer incidence is increasing among younger people in the U.S., and falling among older people,” says the lead author of the study, Maria Constanza Camargo, PhD, of the division of cancer epidemiology and genetics at the National Cancer Institute. “Although stomach cancer in general is more common in men, the increases were more pronounced among women,” she says. “We also noticed that more of the tumors involved the midsection of the stomach. If current patterns continue, forecasting models predict two notable reversals by 2030: Overall incidence will no longer be decreasing, and female incidence will exceed male incidence rates.” The findings even suggest that a new type of stomach cancer has emerged, Dr. Constanza says. “The classic presentation of a noncardia stomach cancer patient is an older man with a tumor located in the lowest part of the stomach. Our research suggests that in the future, many patients with this disease may fit a different demographic,” she says. “These differences are so striking that we call them the ‘changing face of gastric cancer.’”
Could an Uptick in Antibiotic Use Be the Culprit?
Constanza and her colleagues analyzed data on stomach cancer incidence in the United States and found that between 1995 and 2003, noncardia gastric cancer fell in the general population by 2.3 percent per year. However, when looking at cancer incidence by age, they found that rates for Americans under age 50 increased 1.3 percent per year. Women born in 1983, for example, had a twofold higher incidence of noncardia gastric cancer compared with women born in 1951. Noncardia gastric cancer has two primary causes, Constanza says. It can be caused by a bacterium called Helicobacter pylori, a type of infection in the stomach, or by immune gastritis, a disorder in which the immune system attacks the lining of the stomach. Rates of Helicobacter pylori, or H. pylori as it is commonly known, have declined in the U.S. over the past century, but cases of autoimmune gastritis have increased. The increasing cases of noncardia gastric cancer may reflect changes in antibiotic prescribing patterns in the last half century, Constanza says. The uptick in cases in people younger than 50 began in the 1950s, when antibiotics became much more widely prescribed. Antibiotics, she notes, can influence the balance of healthy microbes in the intestines. The changes could trigger autoimmune gastritis, which increases the risk of cancer. Women are prescribed antibiotics more often than men, the authors noted. “Use of antibiotic medications can disrupt the native microbiome of the stomach, which conceivably might lead to autoimmune gastritis and subsequently to stomach cancer,” Constanza says.
A Cancer Often Diagnosed Too Late
More research is needed to understand why noncardia gastric cancer is increasing in younger Americans, she says. However, the trend is particularly troubling in light of the severity of the disease. Noncardia gastric cancer is often diagnosed when the cancer is already advanced. Successful treatment is difficult then, she says. The five-year survival rate of all U.S. patients with stomach cancer is about 31 percent, according to the American Cancer Society. Patients diagnosed with the disease should seek a second opinion to make sure they get the most appropriate treatment, Constanza says. “If possible, patients should be evaluated at a comprehensive cancer center to ensure that the most up-to-date treatments are considered. Some patients may also qualify for clinical trials evaluating new therapies.”
