Long-term Outcomes of Chronic Hepatitis C Patients Post Sofosbuvir-based Treatment

Main inclusion criteria: For Sofosbuvir-based therapy observational group: * Patients ≥ 20 of years who had ever participated in parent studies, GS-US-337-0131 (NCT02021656) or GS-US-334-0115 (NCT02021643) * Patients who had received at least one dose of sofosbuvir-based therapy in the parent studies. Who IFN-based therapy historical controls, matched with sex, age, level of liver fibrosis and virological response: * Patients ≥ 20 of years who had received pegylated interferon plus ribavirin therapy with match of sex, age, level of liver fibrosis and virological response * Patients who have ever participated study will be collected as historical control. Main exclusion criteria: * Patients not qualified by the main inclusion criteria were excluded. For Sofosbuvir-based therapy observational group: * Patients \< 20 of years * Patients who are unwilling to participate the current study * Patients who had never participated in parent studies, GS-US-337-0131 (NCT02021656) nor GS-US-334-0115 (NCT02021643) * Patients who had never received at least one dose of sofosbuvir-based therapy in the parent studies. Who IFN-based therapy historical controls: * Patients \< 20 of years * Patients who are unwilling to participate the current study * Patients who had never received pegylated interferon plus ribavirin therapy * Patients who did not participate study