Tenofovir alafenamide (TAF) has been approved to prevent HBV reactivation for HBsAg-positive cancer patients receiving chemotherapy. However, the real-world effectiveness and safety of TAF for cancer patients was lacing. Therefore, we conduct a prospective single arm study to evaluate the efficacy and safety of TAF as a prophylactic antiviral agent for HBsAg-positive cancer patients receiving chemotherapy.

This prospective single arm study would be conducted in Taiwan. Patients who fulfill the inclusion criteria, will receive TAF before the initiation of systemic chemotherapy. Based on the guidance of NHI in Taiwan, prophylactic anti-viral agent should be prescribed within 7 days before chemotherapy and would be discontinued at 6 months after cessation of chemotherapy. The duration of TAF prophylaxis would be followed the guidance of NHI in Taiwan, however, the end of our observation would be at week 48 after TAF use. Patients will receive regular follow up at week 4, 12, 24, 36 and 48 (for T-bil, AST, ALT, creatinine, HBsAg, HBV DNA) till 1 year and the outcome will be collected. Platelet and HBcrAg would be examined at enrollment, 24 weeks and 48 weeks. HBeAg and anti-HBeAg will be examined at enrollment and 48 weeks.

Inclusion Criteria:

• Adult patients (age ≥20) with positive HBsAg who are prepared to receive systemic chemotherapy
• The presence of HBs antigen should be confirmed within recent two years
• The patients who could receive systemic chemotherapy in 4 weeks

Exclusion Criteria:

• Patients with poor performance status (Zubrod-ECOG ≥ 2 or Karnofsky score ≤ 70)
• Patients with cirrhosis
• Patients had eGFR lower than 15 ml/min/1.73m2 and didn't receive dialysis
• Patients had exposure to any NUC or interferon within 6 months before chemotherapy
• Patients were co-infected with HCV or HIV
• Allergy history to any tenofovir-based medication
• Pregnant woman
• Unable to sign inform consent