The purpose of this study is to determine whether preemptive nucleoside analogue therapy or regular virologic monitoring is the preferred method in management patients with prior exposure to hepatitis B vius (HBV) and undergoing rituximab-containing chemotherapy.

Occult hepatitis B virus (HBV) reactivation has been documented in patients undergoing rituximab-containing chemotherapy who are hepatitis B surface antigen (HBsAg)-negative but with serologic evidence of prior exposure to HBV. However detailed prospective studies documenting the incidence of reactivation and the virologic and serologic kinetics of reactivation are lacking. The investigators prospective study proposes to follow-up 70 such patients with all serologic and virologic parameters monitored every 4 weeks. Patients with detectable HBV DNA will be started on nucleoside analogue therapy. The optimal method and duration of monitoring will also be determined from our study.

Inclusion Criteria:

• Documented HBsAg-negative with or without antibody to hepatitis B surface antigen (anti-HBs)
• Documented anti-HBc (total)-positive

Exclusion Criteria:

• Concomitant liver diseases including chronic hepatitis C and D infection, Wilson's disease, autoimmune hepatitis, primary biliary cirrhosis and primary sclerosing cholangitis.
• Significant alcohol intake (>30 grams per day)

Patients with B-cell lymphomas or chronic lymphocytic leukaemia referred to Queen Mary Hospital for rituximab-containing chemotherapy