Corresponding author. E-mail address: zeng.zhaochong@zs-hospital.sh.cn (Z.-C. Zeng). 1

Background and purpose: This study aims to evaluate whether dosimetric parameters affect the intrahepatic outfield recurrence or distant metastasis-free survival following the stereotactic body radiation therapy (SBRT) in patients with hepatocellular carcinoma (HCC).Materials and methods: A total of 76 patients with HCC who were treated with SBRT from January 2015 to May 2020 were included in this retrospective study. The main clinical endpoints considered were intrahepatic outfield free survival (OutFFS) and distant metastasis-free survival (DMFS). The target parameters and the liver were documented including tumor diameters, gross tumor volume (GTV), Liver minus GTV volume (LGV), and Liver minus GTV mean dose (LGD). Multivariable Cox regression with forward stepwise selection was performed to identify independent risk factors for OutFFS and DMFS. Maximally selected rank statistics were used to determine the most informative cut-off value for age and LGD.Results: The median follow-up was 28.2 months (range, 7.7-74.5 months). LGD higher than 12.54 Gy [HR, 0.861 (0.747-0.993); p = 0.040] and age greater than 67-year-old [HR, 0.966(0.937-0.997); p = 0.030] are two independent predictors of OutFFS, previous TACE treatment [HR, 0.117(0.015-0.891); p = 0.038] was an independent predictor of DMFS.Conclusions: The results of this study suggested that the higher the dose received by the normal liver (greater than 12.54 Gy) the better the intrahepatic out-field recurrence-free survival (RFS) rate. Further study is warranted to confirm and to better understand this phenomenon.