262 EPIDEMIOLOGY OF GASTRIC CANCER WITHIN NEW MEXICO

Introduction In the United States, the incidence of gastric cancer has been steadily declining. Much of this reduction is due to a decline in cancers of the intestinal type. Within the U.S., variations in gastric cancer incidence exist among different ethnic groups. Hispanics and American Indians have an increased risk of developing gastric cancer compared to non-Hispanic whites (NHW). The aim of the present study was to compare the trends in gastric cancer incidence and histologic type among New Mexico9s unique tri-cultural population of American Indians, Hispanics, and NHW between 1973 and 2001. Methods Using data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute, age-adjusted and age-specific incidence rates by ethnic group and gender were calculated for gastric cancers diagnosed in New Mexico between 1973 and 2001. Trends in the two main histologic types of gastric cancer according to the Lauren classification, intestinal and diffuse, were analyzed. Results A total of 3206 cases of gastric cancer were reported in New Mexico between 1973 and 2001. Overall age-adjusted incidence rates were highest for American Indians followed by Hispanics and NHW throughout the study period. There was a decline in overall age-adjusted incidence rates of gastric cancer for all three ethnic groups. The decline was highest for American Indians (from 24.7 to 13.3 per 100,000) followed by Hispanics (from 21.4 to 12.9 per 100,000) and NHW (from 7.9 to 5.2 per 100,000). For each of the ethnic groups, age-adjusted incidence rates were higher in males than females. The greatest decline in age-adjusted incidence rates was seen in American Indian males (from 34.3 to 16.5 per 100,000). The age-specific incidence rates decreased over time among all groups, with the exception of American Indian females aged 50-59 (from 4.1 to 15.9 per 100,000) and 60-69 (from 17.5 to 29.7 per 100,000). The incidence of gastric cancer increased with age for each of the ethnic groups. The intestinal type of gastric cancer was more common than the diffuse type. The percentage of intestinal-type gastric cancers declined over time, while the percentage of diffuse-type gastric cancers increased, irrespective of ethnic group or gender. The intestinal type was more common in males than females for each of the ethnic groups. Conclusions Gastric cancer incidence rates have steadily declined among New Mexico9s three major ethnic groups over the past 28 years. The greatest rate of decline has been observed within the American Indian population, particularly the males.The percentage of diffuse-type gastric cancers has progressively increased, while the percentage of intestinal-type gastric cancers has progressively decreased.