Dose to cardiac substructures and cardiovascular events in esophageal cancer patients treated with definitive radiotherapy.

Introduction: While there is a growing amount of data on the cardiac toxicity of radiotherapy (RT) in relation to its impact on cardiac sub-structures (CSS), there are only few studies addressing this issue in patients followed for esophageal cancer (ESOC). We aimed to evaluate the association between independent parameters of dose received by CSS and major cardiac events (MACEs) in this population.

Materials and methods: We retrospectively analyzed 122 patients treated with exclusive RT or chemo-RT for ESOC. Heart and CSS i.e. right atrium, left atrium (LA), right ventricle, left ventricle and myocardium, have been automatically segmented, and dose volume histogram were extracted. Cardiac events were collected focusing on the occurrence of MACEs of grade 3 or higher (G3+) and grade 4 or higher (G4+) according to the CTCAE v5.0.

Results: With a median follow-up of 21.9 months and in a population of high to very high cardiovascular risk (95.5%), 21 (17.2%) and 9 (7.4%) patients had G3 + and G4 + MACEs with a respective median time to event of 13.05 and 9.8 months. After multivariate analysis and among all heart and CSS-based dosimetric features, only the volume of LA receiving 15 Gy or more (V15LA) remained significantly associated with the G3 + and G4 + MACEs. The use of volumetric modulated arctherapy significantly reduced V15LA compared with 3D conformal RT.

Conclusion: In a cohort of ESOC patients treated with exclusive RT, incidence of MACEs was associated with V15LA, underlining the importance of CSS. These high cardiovascular (CV) risk patients should benefit from standard CV assessment and strict control of their risk factors.