ESTRO 2024 - Abstract Book

S5144

Physics - Radiomics, functional and biological imaging and outcome prediction

ESTRO 2024

Cardiac dosimetry and correlation with poorer survival in breast cancer patients

Julio Montoya 1 , Paola Caprile 1 , Daniela Cornejo 1 , Ignacio Espinoza 1 , Tomás Merino 2 , Francisco Acevedo 2 , Esteban Barnafi 3 1 Pontifical Catholic University of Chile, Institute of Physics, Faculty of Physics, Santiago, Chile. 2 Pontifical Catholic University of Chile, Department of Hematology-Oncology, School of Medicine, Santiago, Chile. 3 Pontifical Catholic University of Chile, Faculty of Medicine, Santiago, Chile

Purpose/Objective:

Radiation therapy (RT) has a crucial role in the management of breast cancer (BC). Recent evidence suggests that high doses delivered to the heart and its substructures are associated with potential heart diseases and may result in excess mortality (Díaz-Gavela et al., 2021; McWilliam et al., 2020). Our aim is to study the correlation between the dose administered to different cardiac substructures and survival over time, and identify dose thresholds that are predictive of early mortality.

Material/Methods:

Since most BC treatments in Chile include RT (Sung et al., 2021), it is important to study and evaluate the correlation between the dose administered to cardiac substructures and the survival of these patients in a local cohort. An open source program (Finnegan et al., 2017) was employed to auto-segment the heart, its cavities, valves, great vessels and coronary arteries from the RT planning CT images for 143 control and 56 deceased patients. Mean and maximum dose, equivalent in 2-Gy fractions (EQD2), and dose-volume histogram were obtained to each substructure and combined cardiac regions. Additionally, calcifications in the coronary arteries were estimated using a thresholding method (Agatston et al., 1990). Survival analyses using the calcium scores, clinical information and dosimetric parameters of cardiac regions were performed.

Results:

Multivariate regression analysis showed that the maximum dose to the combined cardiac region encompassing the right atrium, right coronary artery, and ascending aorta, age at RT, calcium score, and cancer stage T were significant factors associated with survival over time in our cohort, with hazard ratios of 1.03 (95% CI 1.01-1.06; p = 0.0161), 1.02 (95% CI, 1-1.04; p = 0.0471), 1.03 (95% CI 1.01-1.06; p = 0.003), and 4.18 (95% CI 2.79-6.26; p < 0.001), respectively, whereas cardiac mean dose, V5 and V30 showed no significance. Furthermore, survival curves were plotted, demonstrating that the cohort receiving a maximum EQD2 to the combined region greater than 7 Gy showed lower survival (log-rank p = 0.006).

Conclusion:

The application of this methodology in BC patients validates the maximum dose to the combined cardiac region as an important predictor of premature death. A maximum EQD2 of 7 Gy was obtained as a dose limit for further research.