Optimal timing of antiviral therapy for patients with malignant tumor who presented with hepatitis B reactivation during chemotherapy and/or immunosuppressive therapy.

: Hepatitis B virus (HBV) reactivation may occur with chemotherapy and/or immunotherapy. Antiviral prophylaxis is recommended for all patients who are hepatitis B surface antigen (HBsAg)-positive during chemotherapy and/or immunosuppressive therapy. However, the optimal timing of antiviral therapy before chemotherapy and/or immunosuppressive therapy is not fully elucidated. : We retrospectively evaluated 446 HBsAg-positive patients who underwent chemotherapy and/or immunosuppressive therapy. The cumulative rates of HBV reactivation were evaluated using the Kaplan-Meier method and were compared using the log-rank test. The risk factors of HBV reactivation were examined via univariate and multivariate analyses using the Cox proportional hazards model. : The cumulative HBV reactivation rates of patients who received antiviral therapy before chemotherapy and/or immunosuppressive therapy were significantly lower than those of patients who received antiviral therapy after chemotherapy and/or immunosuppressive therapy ( = 0.002). The incidence of HBV reactivation was significantly different between patients who received antiviral therapy at least 1 day before chemotherapy and/or immunosuppressive therapy and those who did not ( = 0.006). No significant difference was observed in the HBV reactivation rates between patients who received antiviral therapy at least 2 days ( = 0.310), 3 days ( = 0.494), and 1 week ( = 0.655) before chemotherapy and/or immunosuppressive therapy and those who did not. The multivariate Cox proportional hazards model showed that women had a lower risk of developing HBV reactivation than men ( = 0.025). The use of the prophylactic antiviral agent entecavir, compared with lamivudine and telbivudine, was associated with the decreased risk of developing HBV reactivation ( = 0.002). : HBsAg-positive patients who received preemptive antiviral therapy after chemotherapy and/or immunosuppressive therapy had a high risk of developing HBV reactivation. However, it is not necessary for patients to receive antiviral therapy at least 1 week before chemotherapy and/or immunosuppressive therapy.