In addition, our results are similar to other reports stating that response to radiotherapy was associated with better survival. The median OS of patients with objective response in our series was better than that in most previous studies. The difference in the response rates and survival between our study and others may be caused by different radiation techniques, variation in dose schedules, different response evaluation criteria, as well as heterogeneous eligibility criteria for radiotherapy. The majority of previous reports of 3DCRT for HCC used 1.8�C 3.0 Gy daily to achieve total doses of 30�C60 Gy. However, at present, the optimal dose fractionation schedule for SBRT is still unclear. Tse et al. reported good outcomes for unresectable HCC and intrahepatic cholangiocarcinoma treated with SBRT in six fractions administered during two weeks. Therefore, we adopted this dose schedule for the treatment of PVTT/IVCTT in our study. Our study showed that six-fraction SBRT was well tolerated by HCC patients with PVTT/IVCTT, without the occurrence of related serious toxicities. The incidence of Grade 3 acute toxicity in our cohort was lower than that reported in previous 3DCRT series. Although SBRT is a promising therapeutic strategy for HCC with tumor thrombosis, survival after radiotherapy remains limited due to the high frequency of intra- and extra-hepatic recurrences. In theory, the combination of radiotherapy and systemic therapy may provide clinical benefits for patients with PVTT/IVCTT. Sorafenib, an orally active multi-kinase inhibitor, is the only systemic agent that has demonstrated an improved OS in HCC patients. In the current study, 14 patients received combining therapy of sorafenib and SBRT. The group that received this treatment showed a favorable trend in median survival; however, it was not statistically significant. The limited number of patients who received sorafenib in our study may affect the analysis of its therapeutic efficacy; thus, a prospective study addressing this combination is warranted. Robotic non-isocentric dedicated linac systems are widely used for SBRT in the thoracic and abdominal regions. However, current clinical experience with VMAT-based SBRT is still scarce. A unique feature of this study is the combination of SBRT with VMAT, which is a new development in multileaf collimator-based linac radiation delivery. VMAT is a novel extension of the standard IMRT technique, allowing dose AbMole GSK 650394 delivery with simultaneously varying gantry speed, MLC shape, and dose rate. The major advantages of VMAT over classic IMRT are the lower number of MUs and the higher delivery efficiency, with a reduction of 35�C61% in treatment time. The average treatment time was 3.960.6 min for VMAT in our study, which is similar to that reported by Scorsetti et al.. Taking into account the plan quality, treatment efficiency, and delivery accuracy, VMAT-based SBRT can be considered clinically feasible for the treatment of HCC with PVTT/IVCTT.