In the past decade, radiotherapy has gradually become a treatment option for HCC patients and is currently a standard in several guidelines. Klein and Dawson  concluded that SBRT in HCC can have comparable results with other therapies and suggested that it might be offered as a treatment option for early stage HCC patients or patients not eligible to other ablative procedures. SBRT uses up to five fractions utilizing a steep dose fall-off enabling the delivery of high dose to the target volume while limiting the dose to adjacent normal tissue.
The recent results with SBRT for HCC are very encouraging. Bujold et al.  in two sequential trials, showed a 1-year local control of 87% with a clear association of better outcome with higher SBRT doses, although grade 3 toxicity was observed in one third of the patients. Jang et al.  reported that 2-year local control /overall survival (OS )rates in SBRT treated patients with doses of > 54, 45–54, and < 45 Gy were 100/71, 78/64, and 64%/30%, respectively (p = .009/p < .001). SBRT dose was found to be a statistically significant prognostic factor for OS. A BED 10 of 138.1 (51.1 Gy in 3 fractions) were necessary to achieve 90% probability of 2y local control. Dose fractionation in this study was 45–54 Gy in 3 fractions (BED10 of 112.5-151.2 Gy) in Child-Pugh A patients and 30 Gy in 5 fractions (BED10 of 48 Gy) in Child-Pugh B patients.
The risk of radiation-induced liver disease (RILD) is generally proportional to the mean dose of radiation delivered to normal liver tissue. Sanuki et al. reported 3y survival of 70% in 185 patients treated with 35-40Gy in 5 fractions with grade 3 RILD of 13% .
In our own experience with SBRT for HCC, we reported favorable outcomes using SBRT as definitive treatment or as a bridge to liver transplantation in pts with early stage inoperable HCC . Median prescribed dose to the tumor was 54 Gy (range, 30-54Gy) with median overall-survival for the transplanted patients not reached and 23 months for the patients who were not transplanted. Liver explant revealed 81% response rate (27% complete and 54 partial). Only one patient developed RILD.
This demonstrates that not only is SBRT effective but that it is critical to maximize the therapeutic window in these patients and therefore the importance of the best planning technique.
There is no large-scale trial for assessment the best radiation planning technique for HCC SBRT both for target coverage and normal tissue avoidance.
There are studies which compered VMAT versus IMRT in radiotherapy treatment for hepatocellular carcinoma in conventional fractionated radiotherapy. (50-54Gy using 1.8 -2 Gy /day) [10, 11]. VMAT and IMRT was shown to be significantly better CI (0.84 ± 0.05, 0.83 ± 0.04) when compared with 3DCRT (0.72 ± 0.03, p < 0.001) in the treatment of HCC with fractionated regimens(50 Gy/25 fractions). More importantly, VMAT showed significant improvement with regard to HI, lower MUs and shorter delivery time compared to IMRT .
Park et al. using prescription dose of 54gy in 30 fractions has reported that the CI of VMAT (1.0 ± 0.008) was significantly better than that of IMRT (1.1 ± 0.03, p < 0.0001) .
In reviewing studies of SBRT delivery techniques in other tumors, such as lung cancer, pancreatic cancer ,spinal and abdominal metastases, IMRT and VMAT for SBRT and compared those techniques to 3D -CRT with improvement in dose conformality and homogeneity . However, when compared to IMRT dose conformality was greatest with VMAT. Treatment time was markedly quicker with VMAT versus 3DCRT and IMRT. Overall both IMRT and VMAT were able to meet all planning constraints in the studies reviewed; however, treatment efficiency was greatest with VMAT.
However, to our knowledge, this is the first report comparing IMRT to VMAT in SBRT treated HCC patients. Our data suggests that PTV coverage is more conformal with VMAT planning in all pts. VMAT tended to be more effective in all groups for the sparing of normal liver. For pts with PTV volume < = 46 cc the value of VMAT was better for normal liver V15 and CI, for PTV volume > = 46 cc no difference was seen. For right lobe tumor VMAT had lower stomach maximum dose, liver V15, CI.
The study has several limitations; It is a small retrospective study, with different prescribed dose to tumor according to Child type of cirrhosis. In addition, the limited sample size makes it difficult to distinguish variable related to the location of disease. In addition, the relationship between PTV size and volumetric sparing efficiency should be further examined to form a conclusive understanding of this relationship.
In conclusion based on our data we suggest further exploration into the use of VMAT strategies for treatment of HCC with SBRT.