TUESDAY, May 8 (HealthDay News) -- People with the liver disease hepatitis C face a higher risk of developing lymphoma, a cancer of the immune system, new research suggests.
Overall, the risk is almost 30 percent higher, but for a certain type of lymphoma called Waldenstrom's macroglobulinemia, the risk is almost 300 percent higher, according to the study.
"If I had hepatitis C, this would be one more piece of evidence that might make me consider treatment, though hepatitis C treatment can be difficult and is often unsuccessful," said the study's lead author, Dr. Thomas Giordano, an assistant professor of medicine at Baylor College of Medicine in Houston.
"On the other hand," he added, "the risk of these cancers is so small, I wouldn't panic if wasn't getting treatment either. The overall risk is low."
More than 4 million Americans have hepatitis C, and about 26,000 new cases are diagnosed each year, according to the U.S. Centers for Disease Control and Prevention. Lymphomas are cancers that originate in the lymphatic system, a part of the body's immune system. The two most common forms of lymphoma are Hodgkin's and non-Hodgkin's lymphoma. About 8,000 Americans develop Hodgkin's lymphoma and more than 56,000 develop non-Hodgkin's lymphoma each year, according to the Leukemia and Lymphoma Society.
"At least five agents -- four viruses and one bacterium -- are associated with an increased risk of lymphoma, said Dr. Marshall Lichtman, executive vice president for research and medical programs at the Leukemia and Lymphoma Society.
But, Lichtman said he couldn't speculate as to why hepatitis C might increase the risk of lymphoma.
Giordano suspects that the chronic stimulation of the immune system caused by hepatitis C might be contributing to the development of certain lymphomas.
For the new study, Giordano and his colleagues reviewed data from the Veterans Administration. First, they found almost 150,000 veterans with a diagnosis of hepatitis C, and then they matched by age and sex four healthy veterans for each person infected with hepatitis C. Nearly all of the veterans included in the study were male, and the average age was 52.
The researchers found that just under 1,400 people included in the study developed non-Hodgkin's lymphoma and 165 developed Waldenstrom's lymphoma.
The risk of non-Hodgkin's lymphoma was 28 percent higher for those with hepatitis C, and the risk of Waldenstrom's was 276 percent higher, according to the study.
While women only comprised 3 percent of the study population, both Giordano and Lichtman think the results would probably apply to women as well.
The findings are published in the May 9 issue of the Journal of the American Medical Association.
Giordano said there aren't any immediate practical implications from the findings, because there's no standard screening tool for lymphoma. He said the findings may help researchers, and they may alert physicians to think of the possibility of lymphoma in their hepatitis C patients.
Lichtman agreed that lymphoma screening isn't feasible at this point. "Lymphoma is not a disease that can be detected early," he said. "Once it's clinically apparent, it's usually advanced."
Another important point, Lichtman added, is that no one yet knows if the treatments for hepatitis C would reduce the risk of lymphoma, too.
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