Improvement in Coronary Dose Distribution Using Dynamic Swing Arc in Volumetric-modulated Arc Therapy During Esophageal Cancer Radiotherapy

The dose to the left anterior descending coronary artery (LAD) is associated with mortality in patients with esophageal cancer (EC) who underwent radiotherapy. The aim of this study was to compare the dose distributions to the LAD region achieved through volumetric-modulated arc therapy (VMAT) planning using a dynamic swing arc in OXRAY (DSA-VMAT) and conventional coplanar (Conv-VMAT) planning. Ten patients with EC who had undergone radiotherapy (60 Gy in 30 fractions) at our Institution were selected for inclusion in the study. Two virtual plans (DSA-VMAT and Conv-VMAT) were created to compare the dose distributions of the LAD region, heart, lungs, and planning target volume (PTV). All plans were analyzed using paired t-tests. The mean values±standard deviation for 15 Gy to the LAD region (V15) were 10.48±13.04% for DSA-VMAT and 30.28±23.56% for Conv-VMAT. Compared with Conv-VMAT, DSA-VMAT significantly improved V15 of the LAD region (p=0.01). In addition, DSA-VMAT significantly reduced the mean heart dose (8.64±5.37 vs. 11.23±7.37 Gy), heart V40 (17.55±4.76% vs. 20.44±6.06%), lung V20 (14.87±5.93% vs. 17.81±7.70%), and lung V5 (57.27±8.24% vs. 61.15±9.97%) compared to Conv-VMAT (all p≤0.01). In contrast, there were no significant differences between the two groups in PTV dose coverage [D95 (p=0.61), D50 (p=0.62)], or conformity index (p=0.91). Compared with Conv-VMAT, DSA-VMAT improved the dose distribution of the LAD region without impairing the PTV dose coverage. Thus, DSA-VMAT may reduce radiation-induced heart disease in patients with EC without loss of efficacy.