Viral response at 6 months is associated with treatment outcome of adefovir add-on therapy for lamivudine-resistance

Background and Aim: Adefovir add-on therapy is recommended for patients infected with lamivudine-resistant hepatitis B virus (HBV). We aimed to describe the long-term treatment outcome and predictors for good response of adefovir add-on therapy. Methods: A total of 559 chronic hepatitis B (CHB) patients who had been treated for at least 12 months with adefovir add-on therapy due to resistance to lamivudine were retrospectively included. Complete virologic response (CVR) was defined as serum HBV DNA < 9 IU/mL. Viral responses at 6 months were classified as PCR negativity, partial virologic response (PVR, HBV DNA < 2000 IU/mL), or inadequate virologic response (IVR, HBV DNA = 2000 IU/mL). Results: The median duration of follow-up was 31.5 months (range, 1256). The cumulative probabilities of CVR during adefovir add-on therapy were 58%, 70%, 78%, and 80% at 12, 24, 36, and 43 months, respectively. The cumulative rates of resistance to adefovir were 0.4%, 0.8%, and 3.1% at 12, 24, and 36 months, respectively. The only baseline factor associated with CVR (hazard ratio 0.83, 95% confidence interval 0.620.91, P = 0.001) and resistance to adefovir (hazard ratio 1.925, 95% confidence interval 1.133.30, P = 0.017) was serum HBV DNA level. Comparison of the cumulative rates of CVR and resistance to adefovir according to viral response at 6 months showed significant differences among the three groups (P < 0.0001 and P = 0.0005, respectively). Conclusions: Pre-treatment HBV DNA level and viral response at 6 months is associated with treatment outcome for adefovir-add on therapy in lamivudine resistance.