Division of Hepatobiliary and Pancreatic Oncology, National Cancer Center Hospital East, Kashiwa, Japan.
In patients undergoing chemotherapy for the treatment of malignant disease, the reactivation of hepatitis B virus in hepatitis B surface antigen-positive patients has been frequently reported. However, activation has also been reported in hepatitis B surface antigen-negative patients who test positive for hepatitis B core antibody and/or hepatitis B surface antibody, who were thought to have had transient infections and to have been cured. Reactivation has often been reported in patients receiving rituximab-containing regimens and has attracted a lot of attention in recent years. In Japan, 1-3% of patients undergoing chemotherapy are hepatitis B surface antigen-positive, and ∼20-25% of patients are hepatitis B surface antigen-negative with hepatitis B core antibody and/or hepatitis B surface antibody positivity; therefore, about one out of every four patients undergoing chemotherapy may be at risk for the reactivation of hepatitis B virus. In most of the guidelines for hepatitis B virus reactivation, the prophylactic administration of an antiviral drug in hepatitis B surface antigen-positive patients is recommended, and periodic monitoring of hepatitis B virus DNA and the deferred pre-emptive administration of an antiviral drug after conversion to hepatitis B virus DNA positivity are recommended in hepatitis B surface antigen-negative patients who are hepatitis B core antibody-positive and/or hepatitis B surface antibody-positive when chemotherapy has been scheduled. However, numerous issues regarding hepatitis B virus reactivation, including the frequency, the types of anticancer drugs, the cancers that facilitate hepatitis B virus reactivation and the optimal method of management, etc., have not been fully clarified. A variety of well-designed prospective studies are currently under way in both Japan and abroad, and strong evidence of hepatitis B virus reactivation following chemotherapy is anticipated in the future.