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• Exploit the feasibility of using Proton Arc therapy for hepatocellular carcinoma patients. • Investigate the benefit of reducing the possibility of radiation-induced liver diseases. • Explore the feasibility of reducing LET d in adjacent organs at risks. To investigate the potential clinical benefits and dose-averaged Linear Energy Transfer (LET d) sparing, utilizing proton arc plan for hepatocellular carcinoma (HCC) patients in comparison with Intensity Modulated Proton Therapy (IMPT). Ten HCC patients have been retrospectively selected. Two planning groups were created: Proton Arc plans using Monaco ver. 6 and the clinical IMPT plan. Both planning groups used the same robustness parameters. The prescription dose is 67.5 Gy (RBE) in 15 fractions of the Clinical Target Volume (CTV). Robustness evaluations were performed to ensure dose coverage. Normal Tissue Complicated Probability (NTCP) model was utilized to predict the possibility of Radiation-Induced Liver Disease (RILD) and evaluate the potential benefit of proton arc therapy. LET d calculation and evaluation were performed as well. Proton arc plan has shown better dosimetric improvements of most Organ-At-Risks (OARs). More specifically, the liver mean dose has been significantly reduced from 14.7 GyE to 10.62 GyE compared to the IMPT plan. The predicted possibility of RILD has also been significantly reduced for cases with a large and deep liver target where healthy liver tissue sparing is a challenge. Additionally, proton arc therapy could increase the average LET d in the target and reduce LET d in adjacent OARs. The potential clinical benefit of utilizing proton arc therapy HCC varies depending on the patient-specific geometry. With more freedom, proton arc therapy can offer a better dosimetric plan quality in the challenge cases, which might not be feasible using the current IMPT technique. [ABSTRACT FROM AUTHOR]

Aim The purpose of this study was to determine the optimal mean liver biologically effective dose (BED) to prevent radiation-induced liver disease (RILD) in stereotactic body radiation therapy (SBRT). Background The actual mean doses appropriate for liver irradiation in modern radiotherapy techniques have not been adequately investigated, although SBRT is sometimes alternatively performed using fractionated regimens. Materials and methods SBRT treatment plans for liver tumors in 50 patients were analyzed. All distributions of the physical doses were transformed to BED 2 using the linear-quadratic model. The relationship between physical doses and the BED 2 for the liver were then analyzed, as was the relationship between the mean BED 2 for the liver and the planning target volume (PTV). Results A significantly positive correlation was observed between the mean physical dose for the background liver and the mean BED 2 for the whole liver ( P < 0.0001, r = 0.9558). Using the LQ model, a mean BED 2 of 73 and 16 Gy for the whole liver corresponded to the hepatic tolerable mean physical dose of 21 and 6 Gy for Child–Pugh A- and B-classified patients, respectively. Additionally, the PTV values were positively correlated with the BEDs for the whole liver ( P < 0.0001, r = 0.8600), and the background liver ( P < 0.0001, r = 0.7854). Conclusion A mean BED 2 of 73 and 16 Gy for the whole liver appeared appropriate to prevent RILD in patients with Child–Pugh classes A and B, respectively. The mean BED 2 for the liver correlated well with the PTV. [ABSTRACT FROM AUTHOR]