Abstract
158 Background: To prevent cardiac toxicity after chemoradiotherapy for esophageal cancer (EC), decrease of high irradiation dose to the heart without expanding the volume of lung irradiated low dose is needed, but this is not easy under the conventional techniques. Purpose of this study is to investigate the utility of volumetric modulated arc therapy using automated-radiotherapy planning software (auto-VMAT) to solve this issue. Methods: In this simulation study, data of 12 patients with stage I-III ECs previously treated by 3D-conformal radiotherapy (3DCRT) was used. We performed auto-VMAT planning using commercially available ‘Pinnacle3 Auto-Planning’ software. Targets for gross tumor (PTV1) and elective nodal region (PTV2), and organs at risk (OARs: lung, heart, left ventricle, epicardium, left pleura, liver and spinal cord) were delineated. Multi-portal beams were used for 3DCRT and dose description was 40 Gy in 20 fractions for PTV1+2 and 20 Gy in 10 fractions-boost for PTV1. We used the simultaneous integrated boost method for auto-VMAT with a dose description of 60 Gy for PTV1 and 48 Gy for PTV2 in 30 fractions. We performed planning in consideration with decrease of volumes irradiated middle to high dose in left ventricle and achievement of volume irradiated 5 Gy (V5) in lung < 50% as high-priority dose constraints. Results: Prescribed dose coverage of PTVs was equivalent between 3DCRT and auto-VMAT, while auto-VMAT showed better dose-conformity. Auto-VMAT showed a significant decrease of mean dose and V20-V60 in heart, left ventricle and epicardium and significant decrease of V50-V60 in lung and left pleura. V5 in lung was equivalent between 3DCRT and auto-VMAT (46.6±9.6% vs 45.6±4.7%; p = 0.72). Auto-VMAT achieved the V5 in lung < 50% in 10 among 12 patients and the max V5 in lung was 52.5%. Conclusions: Auto-VMAT for ECs achieved better dose conformity of targets, decrease of middle-high dose in heart, left ventricle and epicardium, and equivalent low dose volumes in lung. Auto-VMAT planning brings high quality dose distribution, uniformity of quality of planning, laborsaving and timesaving in treatment planning.
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