Heart base sparing radiotherapy for esophageal cancer: a dosimetric evaluation

Radiotherapy (RT) is an essential component of treatment for locally advanced esophageal cancer, but cardiac toxicity remains a concern, particularly for lower tumors due to their proximity to the heart. Radiation dose to the heart base and cardiac avoidance area (CAA), including the right atrium, sinoatrial node, and aortic valve root, has been associated with arrhythmias, major adverse cardiac events (MACE), and reduced survival. While active heart-sparing (AHS) strategies have demonstrated dosimetric benefits in lung cancer, their feasibility in esophageal cancer remains unclear. This study evaluated the feasibility of heart base sparing RT planning for neoadjuvant chemoradiotherapy for lower esophageal cancer. In this single-center retrospective planning study, 20 patients with distal esophageal cancer previously treated with neoadjuvant chemoradiotherapy (41.4 Gy in 23 fractions) were retrospectively replanned using heart base–guided optimization with intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). Optimization objectives included reduction of dose to the CAA and selected cardiac substructures while maintaining target coverage and conventional organs at risk (OAR) constraints. Dose–volume histogram (DVH) and differential DVH analyses were performed, with DVH parameters compared using the Wilcoxon signed-rank test. Heart base–optimized replanning significantly reduced dose to most cardiac substructures. Mean dose reductions with IMRT/VMAT were observed for the atrioventricular node (28.7 to 18.2/18.3 Gy), aortic valve root (20.2 to 9.5/9.9 Gy), sinoatrial node (13.8 to 6.8/7.6 Gy), right coronary artery (15.6 to 10.3/9.7 Gy), left anterior descending artery (13.7 to 8.7/8.6 Gy), and tricuspid valve (21.3 to 14.2/13.8 Gy). CAA mean dose decreased from 19.5 to 13.3/13.0 Gy, while LAD V15Gy was reduced from 42% to <10%. Differential DVHs demonstrated marked reductions in high-dose exposure (>30 Gy) across most heart base structures. Improvements were achieved while maintaining target coverage and acceptable pulmonary and spinal cord doses. IMRT and VMAT produced comparable cardiac sparing, with VMAT requiring fewer monitor units and showing a tendency toward lower lung V20Gy/V30Gy values. Heart base sparing RT planning strategy using either IMRT or VMAT is feasible in neoadjuvant radiotherapy for lower esophageal cancer and enables substantial reductions in dose to several cardiac substructures implicated in radiation-associated cardiac toxicity. The clinical significance of these dosimetric improvements remains to be determined in prospective studies with long-term cardiac follow-up. Not applicable.