Hepatitis B virus reactivation risk associated with immune checkpoint inhibitors in tumor treatment: a retrospective study.

Background: Hepatitis B virus (HBV) reactivation is a recognized complication of cytotoxic chemotherapy in patients with chronic hepatitis B. However, the risk of HBV reactivation with immune checkpoint inhibitors (ICIs) remains uncertain due to their exclusion from clinical trials. This study aimed to assess the incidence of HBV reactivation in patients with cancer undergoing ICI therapy, exploring associated risk factors.

Methods: This retrospective study included patients with cancer who tested positive for hepatitis B surface antigen (HBsAg). The primary endpoint was incidence of HBV reactivation, whereas the secondary endpoint was occurrence of hepatic adverse events during ICI therapy.

Results: Among the 162 eligible patients (median age 59 years; 85.8% men), HBV reactivation occurred in 4.3% at a median of 13 weeks post-treatment initiation. At baseline, HBV DNA was undetectable in 78 patients; 88 received antiviral prophylaxis, while 74 patients did not. Reactivation rates were 3.5% in HBsAg-positive and 10% in hepatitis B core antibody (HBcAb)-positive individuals, with an overall rate of 4.3%. These rates were 1.1% with prophylaxis and 8.1% without. Twenty-two patients had grade 3-4 hepatitis, and 25 tested HBsAg-negative but HBcAb-positive. No HBV-related fatalities occurred. The absence of antiviral treatment was a significant risk factor for HBV reactivation.

Conclusions: Our study underscores the risk of HBV reactivation in patients with cancer undergoing ICI therapy, especially among those lacking antiviral prophylaxis. Regular HBV DNA testing and antiviral prophylaxis are crucial preventive measures for HBV reactivation. These findings emphasize the importance of monitoring HBV status in patients receiving ICIs.