Resistance mutations to lamivudine and/or ETV was detected only in 3 and 2 patients check details 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 Rapamycin molecular weight 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 MCE 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.