Gastric Intestinal Metaplasia in Ethnic Groups in the Southwestern United States1

The incidence of gastric cancer has declined dramatically in the United States during this century. However, the incidence of gastric cancer among Hispanics, Blacks, and Native Americans remains 2-3fold higher than among Whites in this country. Populations with an increased risk of gastric cancer have predominantly the “intestinal” type of gastric cancer, and intestinal metaplasia is regarded as a histological precursor lesion of this type of gastric cancer. We sought to establish the prevalence of intestinal metaplasia, identify associated epidemiological factors, and improve detection of this lesion in a patient population undergoing clinically indicated endoscopy in the Southwestern United States. Among the 440 patients studied, we observed an overall crude prevalence of intestinal metaplasia of 19%. However, the crude prevalence among Hispanics and Blacks was found to be markedly higher than among non-Hispanic Whites (50% versus 13%). Two biopsy protocols (two biopsies versus four biopsies) were used during this study, with a significantly higher rate of intestinal metaplasia detection under the fourbiopsy protocol. Adjusting for protocol, we found that age and ethnicity were significantly and independently associated with the prevalence of intestinal metaplasia. The odds of intestinal metaplasia diagnosis was significantly higher in Hispanics compared to nonHispanic Whites (P < 0.001), and the prevalence of intestinal metaplasia increased with advancing age (P = 0.0 1 ). The presence of Helicobacter pylon was also significantly associated with the presence of intestinal metaplasia (P 0.02), although the direction of the association differed between Hispanics and nonHispanic Whites. Received 1/7/92. 1 Supported in part by Arizona Disease Control Research Commission 82-1681 and Biomedical Research Support Grant BRSG 2507RR0567521. 2 To whom requests for reprints should be addressed, at Arizona Health Sciences Center, Department of Medicine, Gastrointestinal Section, 1 501 North Campbell, Room 6406, Tucson, AZ 85724. Introduction IMT is considered to be a precursor lesion in the histological pathway from normal gastric mucosa to gastric cancer (1). Gastric carcinoma is classified into two distinct histological subtypes, the “diffuse” and “intestinal” (2). The intestinal type of gastric carcinoma is more frequently found in populations showing increased risk of gastric cancer and has long been recognized to occur in the background of chronic atrophic gastnitis/intestinal metaplasia (3). Intestinal metaplasia develops within areas of chronic atrophic gastnitis and is characterized by the replacement of gastric glands by intestinal-type epithelium. In a fraction of the individuals who develop IM, progression to dysplasia and carcinoma is thought to occur (4). The etiology of IM and intestinal-type gastric cancer remains unclear but presumably involves an interaction of environmental and genetic factors. Diet has been a frequently studied environmental risk factor for gastric carcinoma (4). However, recently the presence of He!icobacter py!ori colonization of gastric mucosa has also been implicated as having a possible role in the development of gastric cancer (5-7), and a high prevalence of H. py!ori infection has been demonstrated in association with precancerous lesions of the stomach (8). Although the overall incidence of gastric carcinoma in the United States has been decreasing over the last 60 years, certain ethnic groups continue to be at increased risk for gastric carcinoma (9). These high risk ethnic populations include Blacks, Hispanics, and Native Amenicans, who have gastric cancer incidence rates 2-3 times higher than those observed among Whites (1 0, 1 1 ). However, the prevalence of IM in these various populations is unknown. We thus conducted a cross-sectional study using upper gastrointestinal endoscopy to determine IM prevalences in an ethnically diverse clinic population in the Southwestern United States. Materials and Methods Between 7/1/89and 7/1/91, subjectswere recruited from among patients at one medical center who were undergoing clinically indicated endoscopy of the upper gastrointestinal tract. Patients were excluded if they were undergoing emergency endoscopy, had active bleeding or lesions predisposing to bleeding (e.g., portal gastropathy or vanices), on had other contraindications to biopsy. During this time period, a total of 440 patients met the entry criteria for the study, which were reviewed and on June 22, 2017. © 1992 American Association for Cancer Research. cebp.aacrjournals.org Downloaded from Table 1 Characteristics of study subjects No. of No. 1%) with intesNo. 1%) positive for subjects tinal metaplasia Helicobacter pylon’ <50 23 3 (13%) 2 0 (0%) 28 1 (4%) 8 4 (50%) 50-69 86 6 (7%) 9 3 (33%) 110 16 (i5%) 24 12 (50%) 70+ 49 4 (8%) 4 2 (50%) 63 1 7 (27%) 1 1 8 (73%) Total 158 13 (8%) 15 5 (33%( 201 34 (17%) 43 24 (56%) ‘ As detected by histological examination of the biopsy tissue. ‘ The total number of subjects (Total n) in each category of age, ethnicity, and protocol is tabulated along with the number nI and percentage (%( demonstrating intestinal metaplasia (IM+( in each category. S Restricted to Hispanics and non-Hispanic Whites. 294 Intestinal Metaplasia in the Southwestern United States Ethnicity White, non-Hispanic 359 47 (i3%) 139 (39%) Hispanic 58 29 (50%) 39 (67%) Native American 1 1 2 (18%) 8 (73%) Black 10 5 (50%) 10 (iOO%) Asian 2 1 (50%) 1 (50%) Age <40 17 2(12%) 12 (71%) 40-49 53 7 (i3%) 21 (40%) 50-59 70 12(17%) 28(40%) 60-69 170 31 (18%) 79 (46%) 70-79 iii 28(25%) 46 (41%) 80+ 19 4(21%) ii (58%) Protocol I (2 biopsies) 1 79 1 9 ( 1 1 %) 79 (44%) II (4 biopsies) 261 65 (25%) 1 18 (45%) approved by the human subjects committee at the Univensity of Arizona. For each patient, key demographic data and the reason for endoscopy were recorded. At the time of endoscopy, the gross appearance of the gastric mucosa was described by the endoscopist performing the procedune. Biopsies were obtained with a standard endoscopic biopsy forceps (Olympus model FB-24K; Olympus Corporation, Lake Success, New York). The gastric mucosa was systematically biopsied according to one of two protocols. Protocol I was used during the first 12 months of the study and required that two biopsies be obtained, both from the angulanis along the lessen curvature. Protocol II was used during the second 12 months of the study and required that four biopsies be obtained: two from the angulanis plus either (a) one biopsy of the antrum 2 cm distal to the angulanis along the lesser curvature and one biopsy of the fundus 2 cm proximal to the angulanis along the lesser curvature on (b) two biopsies of the mid-antrum. Specimens from each patient were pooled and submitted in fonmalin as a single sample and routinely processed. Special stains (Alcian blue to identify goblet cells, Warthin Starry or Giemsa to identify H. pylon) were used at the discretion of the pathologist. IM was defined as the presence of mucin-containing goblet cells of the intestinal type. The presence of paneth cells and endocrine cells at the base of the cnypts was considered supporting evidence (12). The presence or absence of H. pylon by histological examination of the gastric biopsies was also noted. During the study period, a total of 466 endoscopies were performed on the 440 patients recruited; 26 repeat endoscopies were performed on 25 ofthe study subjects. For those subjects who had repeat endoscopies, only results from the initial endoscopy are included in the present report. The data were analyzed using contingency-table analysis, x2 goodness-of-fit tests, and logistic regression analysis (13). Logistic regression techniques were used to model associations between potential predictor variables and the presence of intestinal metaplasia. Odds ratios and 95% confidence intervals were calculated from the resulting model, thereby adjusting for potentially conTable 2 Intestinal metaplasia prevalence’ by age and ethnicity” with stratification by protocol Protocol I Protocol II White Hispanic White Hispanic Total lM+ Total IM+ Total IM+ Total IM+ n n (%( n (%) n n (%( n n (%) founding variables. An odds ratio estimates the proportionate change in the odds of IM corresponding to a 1unit change in a given predictor variable.