This phase 2 trial aims to evaluate the efficacy of entecavir prophylacxis for hepatitis B virus (HBV) reactivation that continues until 6 months after completing CD20 monoclonal antibody therapy in patients with CD20-positive B-cell lymphomas and resolved hepatitis B (negative hepatitis B surface antigen, positive hepatitis B core antibody).

Inclusion Criteria:

• Histopathologically confirmed CD20 positive B-cell lymphoma;
• Plan to receive first-line anti-lymphoma therapy containing CD20 monoclonal antibodies;
• Negative HBsAg, HBV-DNA lower than the detection limit and positive anti-HBC at baseline;
• Total bilirubin less than 1.5X the upper limit of normal (ULN), AST and ALT less than 2.5X ULN;
• ECOG PS: 0~2;
• Estimated survival time >3 months.

Exclusion Criteria:

• Positive HBsAg or HBV-DNA higher than the detection limit at baseline;
• Previous chemotherapy or radiotherapy for lymphoma;
• Other primary liver diseases, such as chronic hepatitis C, hepatitis D, autoimmune hepatitis, Wilson' s disease or primary biliary cirrhosis;
• Pregnant or lactating women;
• History of immunodeficiency, including positive HIV, or other acquired congenital immunodeficiency disease, or history of organ transplantation.