Will Wiping Out Ulcer Bug Stop Stomach Cancer?
Study finds mixed results after eradicating H. pylori
TUESDAY, Jan. 13, 2004 (HealthDayNews) -- A new Chinese study finds that treating people at risk for stomach cancer because they have the ulcer bacterium is not much more effective than treating them with a dummy drug.
The results on ridding the bacterium, Helicobacter pylori, weren't all bad, however. Among patients who had H. pylori, but who did not have precancerous lesions caused by the infection, eradication of the bug did significantly reduce the development of gastric cancer.
The study "proves that H. pylori causes gastric cancer, and that treatment of H. pylori reduces the risk of developing cancer," says study leader Dr. Benjamin Wong, an associate professor of medicine at the University of Hong Kong. However, "in subjects with existing precancerous lesions, the benefit, according to our findings, were minimal, but we need more research on this."
"In high-risk areas or high-risk groups, treatment of H. pylori to prevent cancer should be advocated. This should be done early in life, when the precancerous lesion has not developed yet because once precancerous lesions have developed, the effect of treatment of H. pylori may be lost," Wong adds.
"The connection between H. pylori and gastric cancer is well documented," says Dr. Julie Parsonnet, an associate professor of medicine and health research and policy at Stanford University.
Parsonnet, who co-authored an accompanying editorial, adds, "I don't doubt that H. pylori is a very important cause of stomach cancer. The only question is, is there a reasonable strategy to address it."
H. pylori is the main cause of gastritis and is responsible for about 80 percent of gastric ulcers and about 95 percent of duodenal ulcers. It has also been associated with causing gastric cancer.
In 1994, H. pylori was defined as a grade 1 carcinogen. To prevent gastric cancer, experts have recommended that patients with gastric or duodenal ulcers who also have H. pylori have the ulcer bug eradicated with a regimen of antibiotics.
In the study, Wong and his colleagues randomly assigned 1,630 healthy patients who had H. pylori to a two-week regimen of antibiotics or placebo.
During more than seven years of follow-up, the researchers found 18 cases of gastric cancer -- seven among those who received treatment and 11 among those who received a placebo. This is not a significant difference, Wong's team reports in the Jan. 14 issue of the Journal of the American Medical Association.
However, in a subgroup of patients who did not have precancerous lesions, none of the patients who were treated for H. pylori developed gastric cancer compared with six patients who received placebo.
"What we would like to see is that if you treat everybody to eradicate H. pylori, you can cost-effectively prevent stomach cancer. But what this data shows is that this simple answer may not be possible," Parsonnet says.
Parsonnet speculates the follow-up of the patients was not long enough, and that seen over a longer period of time H. pylori eradication would have proven more effective in preventing gastric cancer.
There are a lot of unanswered questions, Parsonnet adds: "If you treat whole populations, are there going to be side effects? Is there going to be increased drug resistance? Are you going to increase the risk for other diseases? Are you going to prevent other diseases? Are you going to decrease total mortality?"
Parsonnet believes a cheap, effective, noninvasive way of finding those with H. pylori who do not have precancerous lesions needs to be developed. This could identify those who would benefit most from treatment, she says.
More effort should be placed on eradicating H. pylori in developing countries, where it is most prevalent, Parsonnet believes. Gastric cancer is becoming rare in the United States, but it is common in these countries.
"The reason gastric cancer is getting rare in the U.S. is because H. pylori is disappearing rapidly from the U.S." Parsonnet say. "So maybe that should be our focus -- how to get H. pylori to disappear around the world, and focus less on treatment than on prevention."
Dr. Steven Moss, an assistant professor of medicine at Brown University, agrees with Parsonnet. "In areas where gastric cancer and H. pylori are very common, it is a big public health issue," he says.
In the United States, Moss believes that screening for H. pylori in high-risk immigrant communities might be an effective way of preventing stomach cancer.
Moss says other studies are going on in Asia, and they may show a stronger connection between treating the bacterium and preventing stomach cancer.
Dr. David Y. Graham, a professor of medicine and molecular virology at Baylor College of Medicine, comments that "H. pylori causes gastric cancer, and if treated early enough can prevent gastric cancer."
"Eradication of H. pylori would eliminate the second most common cancer in the world," he adds.