Eradication Rate of Helicobacter pylori in a Mexican Population at High Risk for Gastric Cancer and Use of Serology to Assess Cure Alejandro Mohar, M.D., D.Sc., Catherine Ley, Ph.D., Jeannette Guarner, M.D., Roberto Herrera-Goepfert, M.D., Luz-Sa ´nchez Figueroa, David Halperin, M.D., † and Julie Parsonnet, M.D. Instituto Nacional de Cancerologı ´a, Mexico City, Mexico; Instituto de Investigaciones Biome ´dicas, Universidad Nacional Auto ´noma de Me ´xico, Mexico City, Mexico; Stanford University School of Medicine, Stanford, California; Centers for Disease Control and Prevention, Atlanta, Georgia; and El Colegio de la Frontera Sur, Chiapas, Mexico OBJECTIVES: Helicobacter pylori causes gastric adenocarci- noma. We assessed the success of H. pylori eradication therapy in a medically underserved population in Chiapas, Mexico, that is at high risk for gastric cancer risk. METHODS: Healthy volunteers with both antibodies to CagA and gastrin levels 25 ng/ml were randomly assigned to receive either a combination of omeprazole, amoxicillin, and clarithromycin or matched placebo for 1 wk. Endoscopy with seven biopsies was performed at baseline, at 6 wk, and 1 yr after treatment. Treatment success was defined as loss of H. pylori by histological analysis. Cure was assessed using change in serology based on the standardized absor- bance of a H. pylori ELISA. RESULTS: H. pylori eradication rates were high (intent-to- treat analysis: 76.3% [95% CI = 68.7– 84.0%] after 6 wk and 76.1% [95% CI = 67.7– 84.6%] after 1 yr; per protocol analysis: 77.8% [95% CI = 70.1– 85.4%] after 6 wk and 75.2% [95% CI = 66.5– 84.0%] after 1 yr). Nine subjects on active treatment and one subject on placebo who were without H. pylori at 6 wk were infected at 1 yr (recurrence rates 10.7% and 33.3%, respectively, p = 0.31). Median changes in standardized absorbance at 1 yr were 47% and 1% for successfully and unsuccessfully treated patients, respectively. A 10% decline in standardized absorbance after 1 yr had 84% sensitivity and 100% specificity for H. pylori eradication. CONCLUSIONS: Even with a short course of treatment against H. pylori, a high rate of eradication rate can be achieved in populations at high risk for stomach cancer. Serum antibodies are useful in assessing efficacy of therapy. (Am J Gastroenterol 2002;97:2530 –2535. © 2002 by Am. Coll. of Gastroenterology) INTRODUCTION Gastric cancer is the second leading cause of cancer death worldwide, killing approximately 750,000 people annually (1). Despite a steady decrease overall in the incidence of gastric cancer, the absolute number of cases is on the rise because of the aging of the world’s population (1, 2). Un- fortunately, the diagnosis of stomach cancer is often made at advanced stages of disease, with an overall 5-yr survival of 15% (3). Economically depressed regions of the world, where endoscopic and radiographic screenings to detect cancer and precancer are often infeasible, suffer dispropor- tionately. Better strategies are needed to prevent the devel- opment of this deadly disease, particularly among high risk populations. H. pylori infection is a cause of both gastric adenocarci- noma and gastric lymphoma (4 – 6). Poor countries have a high prevalence of H. pylori starting in early childhood, and an almost universal infection in adulthood (7–9). Because of the association of H. pylori infection with malignancy, ef- forts have been made to evaluate the effects of H. pylori eradication on preneoplastic conditions in the gastric mu- cosa. Initial results have been inconsistent and conflicting (10 –12). However, a recent report by Correa et al. described regression of preneoplastic conditions in persons who re- ceived treatment for H. pylori compared with a control group (13). Cure of this infection was associated with a significant increase in the rate of regression of precursor conditions (relative risk = 8.7; 95% CI = 2.7–28.2) (13). This study provides optimism that H. pylori eradication may be an effective method to prevent gastric cancer. Despite the heavy burden of H. pylori–related diseases in developing countries, few studies have evaluated the erad- ication and reinfection rates of H. pylori in these locations (14 –16). In those studies that have been conducted, failure of treatment and recurrence of infection have been common, although optimal therapies have not always been used. Moreover, assessment of cure in areas of limited resources † Dr. Halperin is now deceased. THE AMERICAN JOURNAL OF GASTROENTEROLOGY Vol. 97, No. 10, 2002 © 2002 by Am. Coll. of Gastroenterology ISSN 0002-9270/02/$22.00 Published by Elsevier Science Inc. PII S0002-9270(02)04393-9