Hepatitis C infection increases lymphoma risk

Infection with hepatitis C virus significantly increases the risk of developing certain lymphomas (cancer of the lymphatic system), according to a US study published in the May 8^th edition of the Journal of the American Medical Association.

Investigators speculated that hepatitis C virus, which can cause liver cirrhosis and liver cancer, may also be associated with an increased risk of haematologic malignancies, lymphatic cancer, and cancer of the thyroid. They therefore performed a retrospective analysis of the records of 700,000 individuals who received care from Veterans’ Affairs hospitals between 1996 and 2004.

A total of 146,394 of these individuals were infected with hepatitis C. Patients with hepatitis C were matched with up to four uninfected individuals of the same sex, age, and first date of follow-up visit. In the days before potent anti-HIV therapy became available, non-Hodgkin’s lymphoma was often seen in HIV-infected individuals with very low CD4 cell counts, and it remains an AIDS-defining cancer, although it has become much rarer thanks to effective HIV treatment. Nevertheless, because of the malignancy’s association with HIV infection, HIV-positive individuals were excluded from the study.

The mean age of the study population was 52 years, and 97% were men. Individuals infected with hepatitis C virus were no more likely to have haematological malignancies than uninfected individuals.

However, the investigators did find that infection with hepatitis C virus increased the risk of non-Hodgkin’s lymphoma by 28% (adjusted hazard ratio [HR], 1.28, confidence interval [CI]: 1.12-1.45). They also found that, compared to individuals without hepatitis C, patients with hepatitis C had a significantly increased risk of a very rare form of non-Hodgkin’s lymphoma, Waldenström macroglobulinemia (adjusted HR, 2.76; 95% CI, 2.01-3.79), and of a blood disorder often associated with hepatitis C virus called cryoglobulinaemia (adjusted HR, 3.98; 95% CI, 3.36-4.72).

Although hepatitis C-infected individuals had an increased risk of thyroid problems, they did not have an increased risk of thyroid cancer.

In multivariate analysis, the association between non-Hodgkin’s lymphoma, Waldenström macroglobulinemia, cryoglobulinemia, and thyroiditis remained statistically significant (p = 0.038).

"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. It might then be possible to prevent progression to lymphoma," commented investigator Eric A. Engels, adding, "more research is needed to further clarify the relationship between HCV infection and lymphoma."