The incidence of gastric cancer is expected to fall to rare-disease level in many countries by 2035, though others will continue to experience high rates, researchers report.

"From the clinical point of view, our findings suggest that gastric cancer will remain present, and, simply due to population growth and aging, we are expecting to see more cases of gastric cancer in the future," Dr. Melina Arnold of the International Agency for Research on Cancer, in Lyon, France, told Reuters Health by email.

Several countries have experienced steady declines in gastric cancer and mortality rates, including those with the highest gastric cancer incidences in the world.

Dr. Arnold and colleagues used data from 92 registries in 34 countries, representing 10 world regions, to predict future trends and determine whether gastric cancer is on its way to becoming a rare disease.

Current gastric cancer incidence varied more than eightfold across countries, with the highest rates in Japan and South Korea and the lowest rates in North America and Europe.

Rates have been falling, however, in all included countries except some high-incidence countries, such as South Korea, where rates have been stable over the past few years, the researchers report in Gut.

The trend of decreasing rates is predicted to continue with reductions in most countries, including Japan (from 36 cases per 100,000 person-years in 2010 to 30 cases per 100,000 person-years in 2035).

These trends were somewhat less pronounced in women, and some populations (U.S. blacks, Poland, and France) were expected to experience slight increases in rates through 2035.

Using a threshold of six new cases per 100,000 person-years, gastric cancer will have become rare by 2035 in 16 of 34 countries, compared with 13 countries in 2010.

Despite continued decreases in incidence rates, the absolute number of new gastric cancer cases is expected to increase in the majority of countries. Canada, Cyprus, South Korea, Slovakia and Thailand could see a doubling of new cases, whereas a few other countries (Bulgaria and Lithuania, for example) can expect slight drops in the number of new cases.

Decreasing or stable incidence rates were consistently observed in people aged 50 years and above, but increases in incidence in those younger than 50 years were predicted in 15 of 34 countries, including Belarus, Chile, the Netherlands, Canada and the U.K.

"Contrary to what one might think and what history has shown us (i.e., ongoing decreases in gastric cancer incidence without much 'active' primary prevention), gastric cancer is still a major health issue in many countries," Dr. Arnold said. "This applies to high-incidence countries on the one hand, where incidence is set out to remain high, but also to rising incidence rates in younger generations of typically low-risk countries."

"Both observations are critical for future cancer control planning," she said.

"These changes in the epidemiology of gastric cancer warrant further research and action in terms of cancer control, with primary and secondary prevention being the principal goal given the generally poor prognosis in many parts of the world," the authors conclude.

SOURCE: https://bit.ly/3bCBP4O Gut, online January 30, 2020.