ESTRO 2024 - Abstract Book

S552

Clinical - Breast

ESTRO 2024

A total of 1,005 patients were retrospectively analyzed. All included patients received trastuzumab and underwent postoperative radiation therapy (RT) with a total dose of 50 Gy delivered in 25 fractions. Left ventricular ejection fraction (LVEF) was measured via echocardiography during follow-up, resulting in 2,827 measurements for 844 patients. The primary endpoint of this study is any cardiovascular event (ACVE), including cardiac death, myocardial infarction, heart failure, arrhythmia, and more. Changes in LVEF from baseline measurements were analyzed using a linear mixed model.

Results:

The median follow-up period was 7.53 years. A total of 88 ACVEs were reported. The most frequent types of events were heart failure (N=44), arrhythmia (N=19), and angina pectoris (N=12). The actuarial 8-year rates of ACVE for all patients were 7.3%. Patients with a mean heart dose (MHD) ≥5 Gy had a higher actuarial rate of ACVE than those with MHD <5 Gy (8-year rate 17.2% vs. 6.3%, p<0.0001).

In the univariate analysis, age at diagnosis ≥55 years (hazard ratio [HR] 1.643, p=0.033), hypertension (HR 3.658, p=0.001), and MHD ≥5 Gy (HR 2.887, p<0.001) were associated with an increased rate of ACVE. In the multivariate analysis, hypertension (HR 3.165, p=0.003) and MHD ≥5 Gy (HR 2.950, p<0.001) maintained their statistically significant association with an increased rate of ACVE. For analysis of LVEF measurements, MHD ≥5 Gy was significantly associated with a lower LVEF from the baseline (risk ratio [RR] 0.150, p=0.001) in the linear mixed model. Chemotherapeutic regimen including Adriamycin (RR 0.078, p<0.001), and baseline LVEF (per 1%, RR 0.447, p<0.001), were also associated with a decreased LVEF from the baseline. In contrast, postmenopausal status (RR 3.967, p=0.025) and time from the completion of RT (per 1 month, RR 1.009, p=0.029) were associated with an increased LVEF from the baseline.

Conclusion: