Rituximab carries high risks of hepatitis B virus reactivation in hematologic and rheumatic patients with chronic or resolved hepatitis B

Background and Aim Rituximab therapy is associated with a high risk of hepatitis B virus (HBV) reactivation. We aimed to assess whether the risk of reactivation differed among various underlying diseases and between hepatitis B surface antigen (HBsAg) carriers and patients with resolved HBV infection. Methods We retrospectively analyzed patients with chronic or resolved HBV infection who received rituximab without prophylactic anti‐HBV therapy at a tertiary medical center. The risks of HBV reactivation, hepatitis, and hepatic decompensation were compared between the patients with hematologic and rheumatic diseases. Results There were 78 patients with hematologic diseases and 39 patients with rheumatic diseases included. Among them, 43 (59%) HBsAg‐positive patients and 24 (55%) patients with resolved HBV infection experienced HBV reactivation at a median of 14.6 months after rituximab therapy. After rituximab treatment, the 1‐year HBV reactivation rate among patients with hematologic and rheumatic diseases was 29% and 45% in HBsAg‐positive patients, respectively, while the rates were 38% and 17% in patients with resolved HBV infection. The reactivation risk continued to increase even 2 years after rituximab therapy and was comparable between hematologic and rheumatic patients. A higher baseline HBV DNA level (≥20 IU/mL vs <20 IU/mL) was an independent predictor for HBV reactivation (adjusted hazard ratio [aHR]: 10.9, 95% confidence interval [CI]: 1.1–107) and HBV‐associated hepatitis (aHR: 14.8, 95% CI: 1.4–158). Conclusions Rituximab therapy is associated with a 50–64% risk of HBV reactivation regardless of underlying diseases and HBsAg status. HBV DNA levels should be assessed before initiating rituximab.