Risk of kidney cancer and chronic kidney disease in relation to hepatitis C virus infection: a nationwide register-based cohort study in Sweden.

Chronic hepatitis C virus (HCV) infection is an established cause of liver cancer, and recent studies have suggested a link with kidney cancer. The aim of this study was to evaluate risk of kidney cancer in relation to HCV infection in a nationwide registry-based study of Swedish residents diagnosed with HCV between 1990 and 2006. A total of 43 000 individuals with chronic HCV infection were included, and the mean follow-up time was 9.3 years. Observed kidney cancer incidence and mortality in the cohort were compared with expected values based on the age-adjusted and sex-adjusted rates in the general population. Risk of hospitalization for other chronic kidney disease was also evaluated using Cox proportional hazards regression. No association between HCV infection and risk of kidney cancer was observed [standardized incidence ratio with 1-year lag=1.2; 95% confidence interval (CI): 0.8-1.7]. Risk of hospitalization for noncancer kidney disease was significantly elevated in the HCV cohort, with significantly stronger associations observed among women than among men [hazard ratio=5.8 (95% CI: 4.2-7.9) and 3.9 (95% CI: 3.2-4.8) for women and men, respectively]. Results of this study do not support the hypothesis that chronic HCV infection confers an increased risk of kidney cancer. However, we did find an association between HCV infection and chronic kidney disease, particularly among women. Given inconsistent findings in the literature, it is premature to consider HCV infection to be a risk factor for kidney cancer.