ESTRO 2024 - Abstract Book

S525

Clinical - Breast

ESTRO 2024

Nebreda, Marta Labado Mora, Marta Carranza Pose, Marta Isabel Gnecchi XX, Miguel Antonio Arguello Garcia, Oriana Briz Leon, Victor Manuel Barrondo Azcorra, Maider Sierra Marin, Ariane Montejo Arteche, Francisco Javier Fuertes Velez

Basurto University Hospital, Radiation Oncology, Bilbao, Spain

Purpose/Objective:

One of the primary dose-limiting factors when irradiating the left breast with external radiation therapy is the mean dose to the heart. In addition to this restriction, there are studies that indicate the importance of assessing the dose received by cardiac substructures (left anterior descending artery, left ventricle…) to reduce the probability of a long-term cardiac event. In this study, we have evaluated the dose received by the left anterior descending artery (LAD) in left breast cancer treatments that met the usual dose constraints (mean heart dose < 3.3 Gy).

Material/Methods:

Twenty randomly selected left breast cancer women who received radiation therapy doses ranging from 40.05 to 48 Gy, without deep inspiration breath-hold technique, and with a mean heart dose of < 3.3 Gy were included. The left anterior descending artery volume was contoured on non-contrast-enhanced CT scans, using a cardiac contouring atlas with a vessel diameter of 5 mm. Subsequently, we calculated the maximum dose, V13Gy, and V18Gy received by this cardiac substructure.

Results:

The average mean heart dose for the 20 analyzed patients was 2 Gy (ranging from 0.7 Gy to 3.3 Gy), meeting the established criteria. When analyzing the left anterior descending artery, the average maximum dose was 33.2 Gy (ranging from 5.2 Gy to 41.7 Gy). The average V13Gy and V18Gy were 31.5% (ranging from 0% to 60.2%) and 30.1% (ranging from 0% to 58.8%), respectively. In 60% of the women, the maximum dose, V13Gy, and V18Gy received by the left anterior descending artery were elevated, and exceeded the recommended thresholds from the reviewed studies. These parameters are associated with the risk of experiencing a cardiac event.

Conclusion:

The importance of delineating the volume of cardiac substructures is evident. Even when the mean heart dose is within acceptable limits, the dose to these substructures may be high. If the LAD is contoured, dosimetry can be optimized reducing the dose to this organ. Another option is the use of deep inspiration breath-hold technique to mitigate dose constraints. Additionally, we would like to emphasize the importance of individualized therapy, selecting patients with cardiovascular risk factors for close follow-up, treatment, and care.

Keywords: Cardiotoxicity, Cardiac-dosimetry, Cardio-oncology

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