Jan. 13, 2004 -- Although stomach cancer remains one of the world's five most common cancers among men and women, its incidence has steadily declined in the U.S. over recent decades -- thanks, say experts, to lower rates of helicobacter pylori bacteria infection among Americans.
The link between H. pylori and stomach cancer is well established. Still, H. pylori infection is present in nearly half the world's population, and it's rampant in parts of Southeast Asia, Latin America, and other countries with crowded and less hygienic living conditions. The bacterium is so implicated in stomach cancers that in 1994, the International Agency for Research on Cancer (IARC) classified H. pylori as a group 1 carcinogen -- a definite cause of human cancer.
But the question remains: Will successfully treating those infected with H. pylori with antibiotics reduce rates of stomach cancer?
Not really, suggests the first randomized study to address the issue. After tracking 1,630 patients for more than seven years, researchers at the University of Hong Kong found that overall, there was little difference in stomach cancer rates between people who received active antibiotics to eradicate H. pylori infection and those getting "dummy" pills, which did nothing.
However, there is some good news: Antibiotic H. pylori treatment did seem to reduce later cancer rates -- by about one-third -- in a small group of patients who didn't have precancerous tissues in their stomach when first given the drugs.
"If this holds true (in future studies), treatment in early life, when the stomach does not yet have precancerous lesions, will be better," lead researcher Benjamin Chun-Yu Wong, MD, tells WebMD.
That could be important because H. pylori infection, at least in the U.S., typically occurs in childhood -- and can exist innocuously for decades before causing stomach cancer. This bacterium also raises the risk of peptic ulcers.
Sanitation Key to Reducing Spread
"Most people here are infected by age 5," says Julie Parsonnet, MD, of Stanford University. "It's passed from diapers, children playing with poop, crawling on the floor, and sticking things in their mouths. The way to prevent infection is to wash your hands frequently, especially when you take care of your kids, and to decrease household crowding -- things we're doing anyway."
That is why H. pylori infection is disappearing in the U.S. population "at astronomical rates," she says. "The reason why this study was done in China was because H. pylori is not common in the U.S., but it is there." Conversely, stomach cancer is widespread in China, Japan, and Latin America, but not in America.
Besides healthier living conditions here, a diet high in antioxidant-rich fruits and vegetables may also prevent H. pylori infection, says Parsonnet.Interestingly, although H. pylori can lead to peptic ulcers, she adds that Americans with a history of stomach ulcers seem to have lower rates of developing stomach cancer than do others.
She wasn't involved in Wong's study, but she did provide an accompanying editorial to it. Both are published in this week's issue of TheJournal of the American Medical Association.
"The take-home message of this study is that just treating H. pylori doesn't seem to be the answer for the general population," she tells WebMD. "But for some people, it can work -- and that's why it's complicated."
Wong says that while his "overall result is negative," he attributes this to his study not being long enough -- a fact Parsonnet notes in her editorial.
"With a longer follow-up, we should be able to demonstrate a more significant result," Wong tells WebMD. Still, his findings may suggest the benefit of early H. pylori detection and treatment -- especially for people with a family risk of stomach cancer or living in countries with high cancer rates. "Treatment may be too late if they already have developed precancerous lesions," he says.
Besides H. pylori infection, stomach cancer risk factors include a family history of the disease, smoking, a high-salt diet, and low produce intake.