Incidence of extrahepatic cancers among individuals with chronic hepatitis B or C virus infection: A nationwide cohort study.

This study examined the association between chronic HBV or HCV infection and the risk of extrahepatic cancers. A total of 537 103 adults aged ≥20 years without history of cancer were identified from the Korean National Health Insurance Service-National Sample Cohort between 2003 and 2013. The difference in cancer incidence was compared between those with and without chronic HBV or HCV infection. During 3 854 130 person-years of follow-up (median follow-up: 8.0 years), 19 089 participants developed cancer. After adjusting for sex, body mass index, smoking, drinking, income percentile, residential area and comorbidities, hazard ratios (HRs) for incident extrahepatic cancer were significantly higher in participants with chronic HBV infection (HR: 1.27, 95% confidence interval [CI]: 1.20-1.35), HCV infection (HR: 1.31, 95% CI: 1.16-1.48) or HBV/HCV dual infection (HR: 1.41, 95% CI: 1.31-1.72) compared to participants without HBV or HCV infection. In chronic HBV infection, the cancer risk was higher for haematologic malignancy [HR (95% CI) = 2.46 (1.92-3.15)], gallbladder [1.55 (1.05-2.29)], pancreas [1.52 (1.07-2.15)], stomach [1.39 (1.22-1.58)], lung [1.27 (1.04-1.55)], colorectum [1.21 (1.03-1.42)] and thyroid cancer [1.20 (1.05-1.36)]. In chronic HCV infection, the cancer risk was higher for testis [10.34 (1.35-79.78)], gallbladder [2.90 (1.62-5.18)], prostate [2.51 (1.65-3.82)] and thyroid cancer [1.46 (1.10-1.93)]. In conclusion, chronic HBV or HCV infection was not only associated with an increased risk of liver cancer, but also associated with an increased risk of multiple extrahepatic cancers.