To Compare the Efficacy of a Prophylactic Use of Tenofovir by Duration for the Non-Hodgkin's Lymphoma

Inclusion Criteria: 1. Age of ≥ 18 (Women must not be pregnant or breast-feeding; all females of childbearing potential must have a blood test or urine study during screening to rule out pregnancy. / A woman of childbearing potential must be using an adequate method of contraception to avoid pregnancy throughout the study and for up to 26 weeks after the last dose of tenofovir. / If the Investigator obtains information concerning the pregnancy of a female patient, the Investigator must terminate the study drug immediately in that patient, and report the information to IRB in the same manner as for SAE reporting) 2. CD 20 positive patients with Non-Hodgkin's lymphoma who are planned to receive anticancer treatment with rituximab based chemotherapy and A. ECOG performance status 0-2 B. Adequate renal function: serum creatinine level \< 2 mg/dL (177 μmol/L) C. Adequate hematological function: hemoglobin ≥ 9g/dL, absolute neutrophil count (ANC) ≥ 1,500/μL, platelet count ≥ 75,000/μL, unless abnormalities are due to bone marrow involvement by lymphoma D. Expected residual life ≥ 6 months 3. Serum HBsAg negative, anti-HCV negative, but anti-HBc positive 4. ALT \< 80IU/mL, serum bilirubin \< 3.0mg/dL, unless abnormalities are due to liver involvement by lymphoma or tumor lysis syndrome 5. Individuals who were given and understood detailed explanations about this study, voluntarily decided to participate in the study, and provided written informed consent Exclusion Criteria: 1. Child-Pugh class C 2. Other chronic liver diseases such as autoimmune hepatitis or Wilson's disease 3. Patient who has hypersensitivity to study drug 4. Patient who has galactose intolerance, Lapp lactase deficiency, glucose-galactose malabsorption 5. Patient who is pregnant or on lactating. Or who has plans for pregnant or lactation during study period even the partner of the male patient