B-cell non-Hodgkin's lymphoma and hepatitis C virus infection: a systematic review.

A high prevalence of hepatitis C virus (HCV) infection in patients with B-cell non-Hodgkin's lymphoma (B-NHL) has been reported in some, but not all, studies, and the association showed a strong regional variation. We conducted a systematic review of the prevalence of HCV infection in case series of B-NHL and, when an appropriate control group was available, of the odds ratio of B-NHL associated with HCV infection. A high HCV prevalence in B-NHL was found in southern and eastern Europe, Japan and the southern United States, but not in central and northern Europe, Canada, northern United States, or a few Asian countries. Possible sources of heterogeneity and bias are discussed. The odds ratio of B-NHL for HCV infection was relatively weak, ranging from 2 to 4 in most studies. Thus, even if the observed association were causal, the percentage of cases of B-NHL attributable to HCV infection would be relatively low (10%) also in countries with a high prevalence of HCV infection in the general population, and extremely low in other countries. This may explain apparent inconsistencies between studies. Potential mechanisms of action are also discussed. Copyright 2004 Wiley-Liss, Inc.