Trends in gastric cancer incidence in a well-defined French population by time period and birth cohort.

Epidemiological studies have shown a marked decline in gastric cancer incidence and opposite patterns between proximal and distal sites among different populations. Little is known about trends by histological type. The aim of this study was to analyse the change in gastric cancer incidence patterns by investigating the role of temporal components as determinants of such trends in the population of the Côte d'Or area (France) registered between 1976 and 1995. Gastric cancer incidence decreased over time. There was a decrease in incidence rates for distal cancers (-3.5% P < 0.001 per year in men and -4.6% P < 0.01 in women). In contrast, there was a non-significant increase of proximal cancer incidence in men and in women. Rates of adenocarcinomas decreased, whereas the incidence rates of undifferentiated carcinomas and of other histological types remained quite stable. There was a decrease in cumulative risk throughout the studied cohorts, whereas risk for proximal cancer remained stable and decreased slightly for distal localization. For adenocarcinomas, earlier birth cohorts showed a slight decrease in rates, whereas there was an increase for recent cohorts. Subsite and histological-specific analysis, in revealing different time trends in incidence, suggest, at least partly, different aetiologies for gastric cancer, and future aetiological studies must distinguish proximal and distal cancers.