ANN ARBOR, Mich. -- Gastric cancer, the No. 2 cancer killer globally, often develops as a result of infection with the bacterium Helicobacter pylori, holding out the promise that campaigns to eradicate the bug in high-risk populations could have a significant public health impact.
A newly published article in the Journal of the American Medical Association on the results of a multinational clinical trial reports that one year after treatment with antibiotics for H. pylori infection, disease recurrence rates among patients in six Latin American countries varied significantly by demographic group.
“The results underscore the importance of tailoring gastric cancer prevention programs based upon determinants such as region, age, and gender, rather than a ‘one size fits all’ approach – a common strategy for many disease and cancer prevention programs,” says Douglas Morgan, M.D., M.P.H., of Vanderbilt University.
Morgan and Javier Torres, Ph.D., of the Mexico Public Health Institute (INSP, IMSS), are lead authors on the paper.
The JAMA paper analyzes one-year follow-up data from SWOG S0701, a treatment study of 1,463 H. pylori-infected participants at seven sites in Mexico and Central and South America, the largest such clinical trial of H. pylori eradication ever undertaken. Overall, the three antibiotic regimens tested had a one-year cure rate of about 73 percent.
Researchers found that 11.5 percent of those whose initial antibiotic therapy had appeared to be effective (i.e., they had tested negative at six to eight weeks) were once again H. pylori-positive at one year, either because the initial infection had lingered or because the participant had become reinfected.
The chance of H. pylori recurrence varied significantly across the seven study sites. Patients in Tuquerres, Colombia, for example, were roughly 2.5 times more likely to have their H. pylori recur than were patients in Guanacaste, Costa Rica. The authors suspect regional antibiotic resistance may be to blame, in part, for these observed differences in rates of effectiveness.
Recurrence also varied by gender (women had a higher rate of recurrence), by age (younger adults had a higher rate of recurrence), and by whether participants actually took their antibiotics as prescribed (those who had returned 20 percent or more of their pills after the treatment period had a higher rate of recurrence).
These variations in treatment effectiveness mean that before public health researchers can conduct large-scale gastric cancer prevention trials, “we need to have populations better defined than just ‘H. pylori-positive,’” says Laurence H. Baker, D.O., of the University of Michigan Medical School, who is senior author of the JAMA paper and chair of the SWOG cancer research group, which led the trial. “For example, do patients have evidence of systemic infection or gastritis?”
Baker says there’s much more researchers need to learn before they can come to convincing answers on how, where, and when – and if – a large H. pylori eradication trial in Latin America might be warranted, but he emphasizes the positive takeaway from the S0701 study: “There’s still a large number of people who converted from H. pylori positive to negative and remained that way at one year.”
The international group of researchers also included University of Michigan Health System gastroenterologist William D. Chey, M.D., and medical oncologist Manuel Valdivieso, M.D.
Funding: The S0701 clinical trial was funded by a grant from the Bill & Melinda Gates Foundation (OPP43930), and grants from the National Cancer Institute of the United States supported the SWOG administrative and statistical infrastructure.
Study sites: Santiago, Chile; Túquerres, Colombia; Guanacaste, Costa Rica; Copán, Honduras; Obregón, México; Tápachula, México; and León, Nicaragua
Authors/Reference: Morgan, D.; Torres, J.; Sexton, R.; Herrero, R.; Salazar-Martínez, E.; Greenberg, E.R.; Bravo, L.E.; Dominguez, R.L.; Ferreccio, C.; Lazcano-Ponce, E.C.; Meza-Montenegro, M.M.; Peña, E.M.; Correa, P.; Martínez, M.E.; Chey, W.D.; Valdivieso, M.; Anderson, G.L.; Goodman, G.E.; Crowley, J.J.; Baker, L.H. Risk of recurrent Helicobacter pylori infection one year after initial eradication therapy in seven Latin American communities. Journal of the American Medical Association, 2013 Feb 13;309(6):578-586.
Resources: Original six-week results of the S0701 study: Greenberg, E.; Anderson, G.; Morgan, D.; et al. Lancet. 2011 Aug 6;378(9790):507-14.
SWOG is one of five cooperative groups within the National Cancer Institute’s (NCI’s) National Clinical Trials Network. SWOG designs and conducts multidisciplinary clinical trials to improve the practice of medicine in preventing, detecting, and treating cancer, and to enhance the quality of life for cancer survivors. The more than 4,000 researchers in the group’s network practice at more than 500 institutions, including 23 of the NCI-designated cancer centers as well as cancer centers in almost a dozen other countries. Formerly the Southwest Oncology Group, SWOG is headquartered at the University of Michigan in Ann Arbor, Michigan, (734-998-7140) and has an operations office in San Antonio, Texas, and a statistical center in Seattle, Washington. Learn more at swog.org.
Written by Frank DeSanto