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. 2019 Feb 7;14(1):29.
doi: 10.1186/s13014-019-1234-z.

Is mean heart dose a relevant surrogate parameter of left ventricle and coronary arteries exposure during breast cancer radiotherapy: a dosimetric evaluation based on individually-determined radiation dose (BACCARAT study)

Sophie Jacob  1 , Jérémy Camilleri  2 , Sylvie Derreumaux  3 , Valentin Walker  4 , Olivier Lairez  5 , Mathieu Lapeyre  6 , Eric Bruguière  6 , Atul Pathak  7 , Marie-Odile Bernier  4 , Dominique Laurier  8 , Jean Ferrieres  9   10 , Olivier Gallocher  2 , Igor Latorzeff  2 , Baptiste Pinel  2 , Denis Franck  2 , Christian Chevelle  2 , Gaëlle Jimenez  2 , David Broggio  11
Affiliations

Is mean heart dose a relevant surrogate parameter of left ventricle and coronary arteries exposure during breast cancer radiotherapy: a dosimetric evaluation based on individually-determined radiation dose (BACCARAT study)

Sophie Jacob et al. Radiat Oncol. .

Abstract

Background: Intra-individual heterogeneity of cardiac exposure is an issue in breast cancer (BC) radiotherapy that was poorly considered in previous cardiotoxicity studies mainly based on mean heart dose (MHD). This dosimetric study analyzes the distribution of individually-determined radiation doses to the heart and its substructures including coronary arteries and evaluate whether MHD is a relevant surrogate parameter of dose for these substructures.

Methods: Data were collected from the BACCARAT prospective study that included left or right unilateral BC patients treated with 3D-Conformal Radiotherapy (RT) between 2015 and 2017 and followed-up for 2 years with repeated cardiac imaging examinations. A coronary computed tomography angiography (CCTA) was performed before RT for all patients. Registration of the planning CT and CCTA images allowed delineation of the coronary arteries on the planning CT images. Using the 3D dose matrix generated during treatment planning and the added coronary contours, dose distributions were generated for whole heart and the following substructures: left ventricle (LV), left main coronary artery (LMCA), left anterior descending artery (LAD), left circumflex artery (LCX) and right coronary artery (RCA). A descriptive analysis of the physical doses in Gray (Gy) was performed, Dmean was the volume-weighted mean dose.

Results: Dose distributions were generated for 89 left-sided BC patients (MHD = 2.9 ± 1.5 Gy, Dmean_LAD = 15.7 ± 3.1 Gy) and 15 right-sided BC patients (MHD = 0.5 ± 0.1 Gy; Dmean_RCA = 1.2 ± 0.4 Gy). For left-sided BC patients, the ratio Dmean_LAD/MHD was around 5. Pearson correlation coefficients between MHD and Dmean for delineated substructures were all statistically significant. However, for all substructures, the coefficient of determination R2 indicated that the proportion of the variance in Dmean of the substructure predictable from MHD was moderate to low (in particular R2 = 0.45 for LAD). Among left-sided BC patients with MHD < 3Gy, 56% of patients could nevertheless receive LAD doses above 40Gy (V40 > 0).

Conclusion: Our study illustrates that MHD is not enough to predict with confidence individual patient dose to the LV and coronary arteries, in particular the LAD. For precise radiotherapy-induced cardiotoxicity studies it would be necessary to consider the distribution of doses within these cardiac substructures rather than just the MHD.

Trial registration: ClinicalTrials.gov: NCT02605512 , Registered 6 November 2015 - Retrospectively registered.

Keywords: Breast cancer; Cardiotoxicity; Coronary arteries doses; Heterogeneity in cardiac exposure; Mean heart dose; Radiotherapy.

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Conflict of interest statement

Ethics approval and consent to participate

This study received ethical approval from the French South West Committee for Protection of Persons (ID: CPP2015/66/2015-A00990–69) and from National Agency for Medical and Health products Safety (Reference: 150873B-12). All patients enrolled in the study provided their written informed consent.

Consent for publication

Consent for publication of the individual person’s image was obtained from that person.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
CT dose-planned left tangential breast irradiation showing isodoses and delineated structures: Heart (orange circle), left ventricle (LV), Left anterior descending coronary artery (LAD) and right coronary artery (RCA)
Fig. 2
Fig. 2
Relationship between MHD and mean doses to left ventricle and coronary arteries for left-sided BC patients
Fig. 3
Fig. 3
Relationship between MHD and mean doses to left ventricle and coronary arteries for right-sided BC patients
See this image and copyright information in PMC

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