Noncardia gastric cancer declined among all race and age groups for the past three decades, except for whites aged 25 to 39 years, according to cancer registration data.
Researchers conducted a descriptive study with age-period-cohort analysis of cancer registration data from the National Cancer Institute's Surveillance, Epidemiology, and End Results program. They analyzed noncardia primary cancers of the stomach, excluding leukemia, lymphoma, mesothelioma, or Kaposi sarcoma, in patients ages 25 to 84 years who were grouped into five-year intervals. Race was categorized as white, black, or other (including unspecified). Socioeconomic status was inferred from prevalence of poverty in the county of residence. The study results appear in the May 5 Journal of the American Medical Association.
From 1977 through 2006, there were 83,225 adults with incident primary gastric cancer, including 39,003 noncardia cases. Overall, age-standardized annual incidence per 100,000 population declined during the study period from 5.9 (95% CI, 5.7 to 6.1) to 4.0 (95% CI, 3.9 to 4.1) in whites, from 13.7 (95% CI, 12.5 to 14.9) to 9.5 (95% CI, 9.1 to 10.0) in blacks, and from 17.8 (95% CI, 16.1 to 19.4) to 11.7 (95% CI, 11.2 to 12.1) in other races.
Among whites, age-specific trends varied significantly between older and younger groups (P<0.001 for interaction by age). Incidence per 100,000 declined significantly from 19.8 (95% CI, 19.0 to 20.6) to 12.8 (95% CI, 12.5 to 13.1) for ages 60 to 84 years and from 2.6 (95% CI, 2.4 to 2.8) to 2.0 (95% CI, 1.9 to 2.1) for ages 40 to 59 years. However, it increased significantly from 0.27 (95% CI, 0.19 to 0.35) to 0.45 (95% CI, 0.39 to 0.50) for ages 25 to 39 years, while falling or remaining stable among all age groups of blacks and other races. Age-period-cohort analysis confirmed a significant increase in younger whites (P<0.001).
Among whites, when broken down into successive birth-year cohorts, age-specific incidence decreased through the 1947 cohort, then progressively increased for the 1952 and subsequent cohorts. Specifically, incidence declined by 1.6% per year over the 1932 to 1942 cohorts, then increased by 2.2% per year over the 1952 to 1962 cohorts. The difference between these slopes before and after the 1947 mid-year of birth was 3.9% per year (95% CI, 2.1% to 5.6%; P<0.001 for the slope contrast). The same effect was seen in white men and white women, centered around the 1947 year of birth.
Researchers conjectured the trends are due to changes in Helicobacter pylori infection patterns, the emergence of a new carcinogenic process exposed by the eradication of H. pylori in gastric mucosa, the Epstein-Barr virus' link to a subset of gastric cancer, changes to gastric microbial flora, or the changing role of diet, particularly increasing salt intake.