Efficacy of prolonged entecavir monotherapy in treatment-naive chronic hepatitis B patients exhibiting a partial virologic response to entecavir

Background/Aims: The optimal management of patients exhibiting a partial virologic response (PVR) to entecavir (ETV) has not been determined. The aim of this study was to determine the long-term efficacy of prolonged ETV monotherapy in treatment-naive chronic hepatitis B (CHB) patients exhibiting a PVR to ETV therapy. Methods: This study included 364 treatment-naive CHB patients treated with ETV for >= 48 weeks and who received continuous ETV monotherapy for >= 96 weeks. PVR was defined as a decrease in serum hepatitis B virus (HBV) DNA of more than 2 log10 IU/mL from baseline but with detectable HBV DNA by real-time PCR assay at week 48. Results: Fifty-two of the 364 patients (14.3%) showed a PVR. Among them, 41 patients received continuous ETV monotherapy for >= 96 weeks (median duration 144 weeks, range 96-312 weeks), and 40 of these patients (95%) achieved a virologic response (VR, HBV DNA <20 IU/mL) during prolonged ETV monotherapy (median duration 78 weeks, range 60-288 weeks). The cumulative probabilities of a VR at weeks 96, 144, and 192 from treatment initiation were 78.0%, 92.7%, and 95.1%, respectively. The VR rate was 97.2% (35/36) in HBeAg-positive patients and 100% (5/5) in HBeAg-negative patients. In multivariate analysis, HBeAg positivity (odds ratio [OR], 9.231; 95% confidence interval [CI], 1.03-82.91; P=0.047) and a high baseline HBV DNA level (OR, 0.170; 95% CI, 0.08-0.37; P=0.000) were independently associated with a delayed virologic response. No patient developed genotypic resistance to ETV during follow-up. Conclusions: Long-term ETV monotherapy is effective for achieving a VR in treatment-naive CHB patients exhibiting a PVR to ETV. HBeAg positivity and high baseline HBV DNA level were independently associated with a delayed virologic response.