Medical Health Encyclopedia

H. pylori is specifically strongly associated certain cancers. And, although evidence is inconsistent, some studies have also linked it to a number of non-gastrointestinal illnesses as well.

Stomach Cancers. Stomach cancer, also called gastric cancer, is the second most common cause of cancer worldwide. In developing countries where the rate of H. pylori is very high, the risk of stomach cancer is six times higher than in America. An important 2001 study strongly supported previous work that found a causal link between H. pylori infection and stomach cancer. In the study, uninfected people did not develop stomach cancer. However, the stomach cancer rates for H. pylori-associated conditions were: 4.7% for nonulcer dyspepsia, 3.4% for gastric ulcers, and 2.2% of stomach polyps. Experts now suggest that H. pylori may be as carcinogenic in the stomach as cigarette smoking is in the lungs.

The process most likely starts during childhood. Infection with H. pylori in early years promotes a precancerous condition called atrophic gastritis. This may lead to cancer through the following steps:

• With atrophic gastritis, the stomach becomes chronically inflamed and loses patches of glands that secrete protein and acid.
• Acid protects against carcinogens (substances that cause cancerous changes in cells).
• New cells replace those destroyed, but these new cells do not produce enough acid to protect against carcinogens.
• Over time, then, cancer cells in the stomach may develop and proliferate.

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Onset of H. pylori infection in adulthood poses an even lower risk, since the development of atrophic gastritis takes years and the patient is likely to die of other causes first. Other factors, such as specific genetic strains and diets might also influence a higher risk for stomach cancer. For instance diets high in salt and low in fresh fruits and vegetables have been associated with a greater risk. Some but not all evidence suggests that the virulent H. pylori genetic strain called CagA may also be a particular risk factor for precancerous changes.