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Vienna, Austria

ESTRO 2023

Session Item

Sunday
May 14
16:45 - 17:45
Stolz 2
Radiotherapy and the heart
David Cutter, United Kingdom;
Hamza Alghamdi, Saudi Arabia
Mini-Oral
Interdisciplinary
16:45 - 17:45
Variation in planned heart radiation dose in 5806 breast cancer patients in 2008-2014: A DBCG study
Emma Skarsø Buhl, Denmark
MO-0639

Abstract

Variation in planned heart radiation dose in 5806 breast cancer patients in 2008-2014: A DBCG study
Authors:

Emma Riis Skarsø1,2, Lasse Hindhede Refsgaard3,2, Abhilasha Saini4, Ebbe Laugaard Lorenzen5, Else Maae6, Esben Yates7, Ingelise Jensen8, Karen Andersen9, Kristian Boye10, Louise Wichmann Matthiessen9, Maja Maraldo10, Martin Berg6, Mette Holck Nielsen11, Mette Møller8, Sami Aziz-Jowad Al-Rawi4, Birgitte Offersen3,7,1,2, Stine Sofia Korreman1,2,7

1Aarhus University Hospital, Danish Center for Particle Therapy, Aarhus, Denmark; 2Aarhus University, Department of Clinical Medicine, Aarhus, Denmark; 3Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark; 4Zealand University Hospital, Department of Clinical Oncology and Palliative Care, Næstved, Denmark; 5Odense University Hospital, Laboratory of Radiation Physics, Odense, Denmark; 6Vejle Hospital, University Hospital of Southern Denmark, Department of Oncology, Vejle, Denmark; 7Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 8Aalborg University Hospital, Department of Oncology, Aalborg, Denmark; 9Herlev and Gentofte Hospital, Department of Oncology, Herlev, Denmark; 10Copenhagen University Hospital – Rigshospitalet, Department of Oncology, København, Denmark; 11Odense University Hospital, , Department of Oncology, Odense, Denmark

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Purpose or Objective

In this study, 5806 patients from the Danish Breast Cancer Group (DBCG) RT Nation cohort were collected, with the aim of verifying the effect of DBCG cardiac related guidelines. We evaluated use of gating, dose to the heart and use of different structures for heart avoidance in treatment planning.

Material and Methods

We included clinical structure sets, dose plans and CT scans from 5806 high-risk breast cancer (BC) patients treated with adjuvant radiotherapy (RT) across the nation during 2008-14. To ensure consistency in reporting heart dose, an in-house developed deep learning (DL) model was used to segment heart structures for all patients.

Patients were split into left and right-sided BC. Left-sided patients were split into gated/non-gated crudely with a cut-off lung volume of 1600 mL (estimated on previous studies). Presence of delineated cardiac structures, including heart and left anterior descending coronary artery (LADCA), was registered. It was assumed, that the presence of a structure implied it being used to guide planning.

The original dose distributions were used to score dose to the DL segmented hearts, with these dose metrics: Dmean (MHD), Dmax (D0.027cc), Dmin, V20Gy and V40Gy. Significance was tested using a Mann-Whitney U-test.

Results

In total 3042 left-and 2764 right-sided BC patients were identified, with a MHD in the cohort of 2.56Gy (± 1.44) and 1.23Gy (± 0.91) respectively.  

Two centres delineated only LADCA (all left-sided BC) or no cardiac delineations (all right-sided BC), whereas the remaining five centres delineated the whole heart or both heart and LADCA, table 1.

Comparing patients treated with or without gating, gated patients showed overall lower heart dose (Dmax: 34.8Gy vs. 46.0Gy, p < 0.01).

In gated patients, no significant difference was found between planning with only LADCA or only heart as avoidance structure, with a median heart Dmax at 36.7Gy and 37.2Gy respectively, figure 2. The same tendency was seen in MHD, V20Gy, V40Gy and Dmin. In non-gated patients, significant differences were found between any use of avoidance structures. IMN was delineated in a subgroup of the patients (226/1153) and showed a lower target coverage than for gated patients (CTVn_IMN mean: 39.3Gy vs 47.4Gy, p<0.01), indicating difficulties with meeting the planning objectives.

For right-sided BC patients, a higher heart Dmax and MHD was found for patients with no avoidance structures compared to those with heart or both(p<0.05).

Conclusion

This is the largest real-world evaluation of dose to the heart in a BC patient cohort. Most patients had a low MHD (<4Gy) in agreement with DBCG guidelines. Gated patients had lower MHD compared to non-gated patients. For gated patients (left-sided), no significant difference in heart dose was found between using whole heart only or LADCA only as avoidance structure, validating the flexible choice of planning structure in DBCG guidelines. Differences for non-gated patients were likely related to difficulties meeting planning objectives.