Ask An Expert: H. Pylori and Stomach Cancer

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Ask An Expert: H. Pylori and Stomach Cancer

Question:

Can h. pylori left untreated for years cause stomach cancer?

Answer:

Helicobacter pylori (referred to as h. pylori) is a spiral-shaped bacterium that can live in the stomach and part of the small intestine (the duodenum). H. pylori has been shown to cause peptic ulcers in the stomach and duodenum, and also chronic irritation (gastritis) and atrophy (thinning) of the lining of the stomach.

There is now good evidence that infection with h. pylori is also associated with the development of two different types of stomach tumors: adenocarcinoma (often called gastric cancer) and MALT (mucosa-associated lymphoid tissue) lymphoma. Many clinical studies support these associations: The bacteria have been found in the stomach tissue of people with stomach tumors, and people with these malignancies very often have a positive blood test indicating exposure to h. pylori. Also supporting the connection between h. pylori and malignancy is the finding that MALT lymphoma tumors can shrink and go into remission when the H. pylori infection is treated with appropriate antibiotics.

Despite this success treating MALT lymphoma, it has not yet been proven that treatment of h. pylori infection actually can prevent the later development of stomach cancers or lymphoma. It is not known whether the risk of developing cancer increases the longer you have the infection. Further study is definitely needed. Prevention of these stomach cancers and lymphoma by treating H. pylori infections would be a major breakthrough in this field.

People infected with the h. pylori organism have a two- to six fold increased risk of developing stomach cancer and MALT lymphoma. Over 300,000 new cases of gastric cancer in the world each year are associated with this infection. It is important to remember, however, that most people infected with h. pylori will never develop stomach cancer. No one yet knows whether screening (and appropriately treating) the entire population, people with no symptoms or risks for h. pylori, would be a good way to significantly reduce the number of people who get stomach cancers.

Diana Post, M.D., is an assistant professor of medicine at Harvard Medical School and a member of the Department of Medicine at Brigham and Women's Hospital.

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Last updated:	January 24, 2007