To evaluate the effectiveness and safety of tenofovir for different treatment duration in preventing HBV relapse in patients with malignancies after receiving chemotherapy and off-treatment of chemotherapy.

This study aims to evaluate the effectiveness and safety of tenofovir in preventing HBV relapse in HBV carriers with malignant tumor following chemotherapy. Approximately 100 patients who are planned to receive chemotherapy for malignant tumor will be invited to participate in this trail. A 1 or less 1-week tenofovir prophylaxis treatment should be administered by all subjects prior to the chemotherapy and eligible subjects will be randomly assigned to extend 24-week prophylaxis group A or 48-week prophylaxis group B in a 1:1 ratio at the end of the chemotherapy. The subjects could be stopped or withdrawn from this study earlier if HBV relapses or need to receive another course of chemotherapy respectively. The relapse episode will be followed until 24 weeks after the end of prophylaxis therapy. Data collection will take place at screening, every cyclic visit of chemotherapy, at the end of chemotherapy, and the following prophylaxis period, then every 4 weeks during the follow-up period. Patients in both groups will be treated with tenofovir or other antiviral agent according to investigator judgement when HBV relapse after discontinuation of tenofovir therapy.

Inclusion Criteria:

1. Male or female 18 to 70 years of age

2. Patients with histologically proven malignant tumor planned to receive chemotherapy after enrollment

3. Hepatitis B virus (HBV) carriers who fulfill one of the following criteria:

   seropositive of HBsAg, or HBsAg negative, but Anti-HBc positive with HBV DNA detectable defined as HBV DNA > 20 IU/mL (by Roche Taqman real time assay).

4. Patients with ALT ≤ 2 x ULN (upper limit of normal)

5. Normal Cr mg/dL or eGFR > 80 mL/min

6. Life expectancy > 1 year

7. Willing and able to provide written informed consent

Exclusion Criteria:

1. Females who are pregnant/nursing or with intention to be pregnant within the study period
2. Documented hepatitis C virus (HCV) co-infection
3. Patients with other current major systemic disease such as active infection, significant cardiac disease, poor control diabetes mellitus, osteopenia or osteoporosis that the investigators consider to be significant risk
4. Current use of any hepatitis B prophylaxis medication
5. Decompensated liver cirrhosis
6. Current or previous use of any chemotherapy
7. Use of any investigational product medicine within 1 month prior to the initiation of study treatment