Infection with the hepatitis C virus, already linked to liver cancer and cirrhosis, also increases the risk of developing non-Hodgkin’s lymphoma, a cancer of the immune system, researchers said on Tuesday.
Researchers tracked 146,394 U.S. military veterans infected with the virus and 572,293 veterans who were not, and found that hepatitis C infection boosted the risk for non-Hodgkin’s lymphoma by 20 percent to 30 percent.
Non-Hodgkin’s lymphoma is cancer that originates in the lymphoid tissue that makes up the lymph nodes, spleen and other organs of the immune system, with tumors developing from white blood cells. It is more common in men than women.
Hepatitis C infection also raised by 300 percent the risk for a rare form of non-Hodgkin’s lymphoma called Waldenstrom’s macroglobulinemia. Risk for cryoglobulinemia, involving abnormal levels of certain antibodies in the blood, also rose.
The findings were published in the Journal of the American Medical Association.
The hepatitis C virus causes hepatitis, a disease marked by liver inflammation, as well as liver cancer and cirrhosis.
It is carried through the blood and spread from one person to another through the exchange of bodily fluids — for example, by sharing needles during injection drug use or by sexual contact. It also was spread via blood transfusions before 1990, when screening for the virus began.
“The thought is that hepatitis C is a chronic infection, and as a chronic infection it results in chronic stimulation of the immune system. And these cancers are cancers of the immune system, essentially,” Dr. Thomas Giordano of Baylor College of Medicine in Houston, lead author of the study, said in a telephone interview.
Infection with the hepatitis C virus, also called HCV, came before the development of these cancers and the increased risk was long-lasting, the study found.
“Although the risk of developing lymphomas is small, our research suggests that screening of HCV-infected individuals could identify conditions which may lead to cancer,” co-author Dr. Eric Engels of the National Cancer Institute, part of the U.S. National Institutes of health, said in a statement.
“It might then be possible to prevent progression to lymphoma,” Engels added.
The study looked at patients in U.S. Veterans Affairs health care facilities from 1997 to 2004. All but 3 percent were men, most were white, and their average age was 52.
There are more than 4 million people infected with the hepatitis C virus in the United States, representing 1.6 percent of the population.