Study examines incidence of gastric cancer

The incidence of a certain type of gastric cancer has declined in the last 30 years for all age groups and races, except for whites 25 to 39 years of age, according to a study in the May 5 issue of JAMA.

Gastric cancer is the fourth most common type of cancer and the second most com¬mon among cancer deaths worldwide. While tumors of the cardia, the upper part of the stomach adjoin¬ing the esophagus, may be related to gas¬troesophageal reflux, the majority of noncardia gastric cancers are attribut¬able to chronic mucosal infection by the bacterium Helicobacter pylori, according to background information in a study by William R. Anderson, M.D., of the National Cancer Institute, Rockville, Md., and colleagues.

"Overall, gastric cancer incidence has steadily declined in many countries over the past 50 years or longer. However, overall trends may mask important age- specific differences. Furthermore, the overall decline runs counter to the subsite-specific rise in cardia cancers that may be related to obesity and gastroesophageal reflux," the authors write.

The researchers ana¬lyzed U.S. population-based age-specific data for noncardia gastric cancer, using data from the National Cancer Institute's Surveillance, Epi¬demiology, and End Results Program, which covers approximately 26 percent of the U.S. popu¬lation. From 1977 through 2006, there were 83,225 adults with new primary gastric cancer, including 39,003 noncardia cases.

The authors found that the overall age-standardized annual incidence per 100,000 population de¬clined during the study period from 5.9 to 4.0 in whites, from 13.7 to 9.5 in blacks, and from 17.8 to 11.7 in other races. "Age-specific trends among whites varied significantly between older and younger age groups: incidence per 100,000 declined significantly from 19.8 to 12.8 for ages 60 to 84 years and from 2.6 to 2.0 for ages 40 to 59 years but increased significantly from 0.27 to 0.45 for ages 25 to 39 years. Conversely, rates for all age groups declined or were stable among blacks and other races. Age-period-cohort analysis confirmed a signifi¬cant increase in whites among younger cohorts born since 1952."

"Targeting all cancer cases in residents of defined geographic areas, the large-scale SEER database is broadly repre¬sentative of cancer incidence in the United States as a whole. Further age-specific analyses of noncardia gastric cancer incidence trends for low-risk populations will be informative," the authors conclude.