ESTRO 2024 - Abstract Book

S532

Clinical - Breast

ESTRO 2024

Purpose/Objective:

The association between radiation exposure to the heart and post-radiation cardiac event (PRCE) or major adverse cardiac event (MACE) is widely acknowledged. However, there is still a need to elucidate the impact of various treatment parameters and risk factors these events. This study aimed to identify prognostic factors for PRCE and MACE using institutional registry data.

Material/Methods:

A total of 9,116 breast cancer patients who underwent post-operative radiation (PORT) from 2012 to 2021 were included. Patients who received partial breast irradiation or had persistent cardiac problems during the radiation treatment session were excluded. PRCE was defined as the occurrence of new diagnoses of any ischemic heart disease, coronary disease, heart failure, cardiomyopathy, or pericardial disease, while MACE was defined as cardiovascular mortality, fatal and non-fatal myocardial infarction and unstable angina, fatal and non-fatal heart failure. The cumulative incidence of PRCE and MACE was estimated by competing risk regression analysis, taking breast cancer mortality as a competing risk.

Results:

The cumulative incidence of PRCE at 1, 2, 3, and 5 years was 0.57%, 0.85%, 1.1%, and 1.6%, respectively, while that of MACE was 0.42%, 0.50%, 0.52%, and 0.69%. Competing risk regression analysis identified bilateral irradiation (Hazared ratio [HR] 1.98, 95% Confidence Interval [CI] 1.18-3.30, p=0.009), age (HR 1.05, CI 1.03-1.07, p<0.001), history of heart disease (HR 3.40, CI 1.60-7.22, p=0.001), and use of Herceptin (HR 3.06, CI 2.11-4.45, p<0.001) as significantly associated with PRCE. Regarding MACE, bilateral irradiation (HR 2.83, CI 1.32-6.07, p=0.007), age (HR 1.03, CI 1.01-1.06, p=0.018), BMI (HR 1.08, CI 1.02-1.14, p=0.008), history of hypertension (HR 2.48, CI 1.12-5.26, p=0.025), and use of Herceptin (HR 4.24, CI 2.50-7.18, p<0.001) were statistically significant risk factors. In terms of laterality of radiation treatment, the cumulative incidence of PRCE at 5 years was 1.5%, 1.5%, and 2.6% for right, left, and bilateral irradiation, respectively. Meanwhile, the cumulative incidence of MACE was 0.50%, 0.81%, and 1.2%, respectively.

Conclusion:

Bilateral irradiation, age, and use of Herceptin were significant risk factors for PRCE and MACE in patients receiving PORT for breast cancer.

Keywords: Breast cancer, Major adverse cardiac event

1095

Poster Discussion

Whole Breast versus Partial Breast Irradiation for early-stage breast cancer: the HYPAB trial