Resistance mutations to lamivudine and/or ETV was detected only in 3 and 2 patients this website in the TDF and TDF+ETV groups, respectively, at 48 weeks. None developed additional resistance mutations. None in the TDF group required protocol-defined switch over of treatment. Both treatments were

well tolerated, and safety and adverse event profiles were similar in the two groups. Conclusions: TDF monotherapy showed similarly high antiviral efficacy and safety as TDF and ETV combination therapy during 48 weeks of treatment in patients with ETV-resistant HBV. None developed additional resistance mutations. KEY WORDS: Lami-vudine, Monotherapy, Resistance, Virologic response Disclosures: Young-Suk Lim – Advisory Committees or Review

Panels: Gilead Science, Bayer; Grant/Research Support: Gilead Science, Novartis, Bayer; Speaking and Teaching: BMS Kwan Soo Byun – Advisory Committees or Review Panels: Gilead; Grant/ Research Support: Gilead, BMS, Taiho, Jassen; Speaking and Teaching: BMS Han Chu Lee – Grant/Research Support: Medigen Biotechnology Co., Novartis, Roche, Bayer HealthCare, Bristol-Myers Squibb, INC research, Boehringer Ingel-heim, Taiho Pharmaceutical NVP-BGJ398 research buy Co., Yuhan Co. The following people have nothing to disclose: Geum-Youn Gwak, Byung Chul Yoo, So Young Kwon, Yoon Jun Kim, Jihyun An, Yung Sang Lee Background: Antiviral therapy may reduce HCC risk but it is unclear what the residual risk would be in treated patients. Our aim is to characterize PIK-5 HCC incidence in treated and untreated patients by cirrhosis status, age (< 45 or ≥45), and gender. Methods: In this retrospective cohort study, 3933 consecutive CHB patients were identified at 3 US centers from 1991-2014. Patients were included if they had at least one year of follow-up and treatment-naïve. Exclusion criteria included HCC at initial presentation and the development of HCC within the first year of follow-up. Diagnosis was based on AASLD criteria for HCC and histology or clinical or imaging data for cirrhosis. Annual

incidence was calculated in cases per 1000 person years. Results: We included a total of 3220 patients with 102 incident HCC cases over a median time of follow-up of 4.1 (1-17) years. In multivariate analysis, antiviral therapy was an independent predictor for reduced HCC risk (HR 0.43, 95% CI 0.23-0.79) following adjustment for age, gender, cirrhosis, HBeAg, ALT, and HBV DNA. In cirrhotic men, regardless of age, the treated group had a lower incidence of HCC (Figure 1). For the non-cirrhotic cohort, the effects of antivirals, while beneficial were modest with the exception of men ≥45 years of age. HCC incidence in treated non-cirrhotic patients ranged from 0 to 1.2 cases per 1000 person years among the various age and gender groups compared to 0 to 6.4 per 1000 person years if untreated. HCC incidence in cirrhotic patients still ranged 16.