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Purpose: The purpose of this study is to determine whether a dose-response relationship in stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC) is observed and to identify whether local control or response affects survival outcome. Methods: Between March 2003 and February 2011, 108 patients with 122 lesions were treated with SBRT for HCC. The indications for SBRT were unsuitable for surgery or other ablative therapies and incomplete response of transarterial chemoembolization (TACE). The inclusion criteria of this study are SBRT using 3 fractions and longest diameter ≤ 7.0 cm. Eighty-two patients with 95 lesions were analyzed. Median age was 60 years (range, 39-79 years). Seventy-four patients (90%) had Child-Pugh class A and 8 patients had B7. All patients had one or more TACE and the median number of TACE sessions per patient was 2 (range, 1-14). The median longest diameter was 3.0 cm (range, 1.0-7.0 cm). The median SBRT dose was 51 Gy (range, 33-60 Gy). Results: The median follow-up duration for all analyzed patients was 30 months (range, 4-81 months). Local control and overall survival rates at 2 years after SBRT were 87% and 63%, respectively. The 2-year local control rates for lesions treated with SBRT doses of >54 Gy, 45-54 Gy, and <45 Gy were 100%, 78%, and 64%, respectively (p=0.0087). In multivariate analysis, SBRT dose and age were significant prognostic factors for local control. The 2-year overall survival rates for patients with and without local failure were 27% and 68%, respectively (p=0.0001). In multivariate analysis, SBRT dose and Barcelona Clinic Liver Cancer stage were significant prognostic factors for overall survival. Five patients (6%) experienced grade 3 or higher gastrointestinal toxicity. The estimated SBRT dose to achieve 90% LC at 2 years is 54 Gy in 3 fractions. In selected patients with SBRT dose > 54 Gy and longest diameter ≤ 5.0 cm, the treatment outcomes of SBRT were comparable with those of radiofrequency ablation (RFA). Conclusions: The present study strongly suggests a dose-response relationship in SBRT for HCC. Excellent local control rates are achieved with SBRT dose of more than 54 Gy or greater. Higher local control rates resulted from increasing dose may be survival benefit for inoperable HCC. We suggest SBRT dose of more than 54 Gy, if normal tissue constraints allow. In the patients with small-sized HCC, high-dose SBRT may be as effective and safe treatment modality as RFA. Disclosure: No significant relationships. [ABSTRACT FROM AUTHOR]