Abstract P2-11-06: Analysis of cardiac events among node positive breast cancer (NPBC) patients treated with three-dimensional conformal radiation therapy (3D-CRT)

Background: Regional nodal irradiation (RNI) in addition to the chest wall and/or breast can maximize local regional control and improve overall survival, but has been associated with late cardiac morbidity. We examined NPBC patients treated with RNI using 3D-CT based radiation therapy (RT) to evaluate incidence and type of cardiac events. Methods: Between 2000 and 2007, 156 NPBC patients were treated with RNI following lumpectomy or mastectomy using 3D-CRT. In all cases, treatment target and normal tissue volumes were delineated on treatment CT scans. The heart contour included the left ventricle and the atria. Prescription dose was typically 50Gy in 25 fractions (range 44-54 Gy) to the chest wall and/or breast PTVeval. 37% received a boost to the chest wall and 73% to the lumpectomy cavity. The mean prescription dose to the axilla and supraclavicular lymph nodes was 47.6 Gy (range 43.2 – 54 Gy) and 46.8 Gy to the IMN (range 35.3 – 50.4 Gy). The dose-volume cardiac data and incidence of cardiac events is reported. Results: Median follow-up of surviving patients was 7 years (range, 0.3-10.6). Median patient age was 50 (range, 27-91), 52% were premenopausal, 76% estrogen receptor positive, and 18% were HER-2 positive. The IMN received > 40 Gy in 66%. Chemotherapy was used in 94% of patients, and it was anthracycline-based in 82.3%. At the time of RT, 12.5% smoked, 9% had diabetes, 33% with HTN, and 4.4% had a history of CAD. Average mean heart dose for the cohort was 5.2 Gy (range, 0.2 - 25.3 Gy). Mean cardiac V25 was 5.4% (range, 0-20%), mean cardiac V45 was 1.7% (range, 0-13.3%), and mean maximum cardiac point dose was 45.4 Gy. There was 1 (0.7% of cohort) right sided patient with cardiac events and 8 (5.1% of cohort) left experiencing cardiac events. A total of 18 cardiac diagnoses were experienced among the 9 patients: Coronary artery disease with or without myocardial infarction (4), congestive heart failure (6), cardiomyopathy (3), and arrhythmia (5). Conclusions: The cardiac event rate among these NPBC patients treated with RNI and anthracycline-based chemotherapy was low, but more common in women with left-sided breast cancer compared to right. Additional analysis using 3DCRT volumes are important to validate these findings and better define the dose-volume parameters for cardiac toxicity. Citation Format: Bradley JA, Sparks I, Prior P, Bergom C, Walker A, Wilson JF, Li XA, White J. Analysis of cardiac events among node positive breast cancer (NPBC) patients treated with three-dimensional conformal radiation therapy (3D-CRT) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-11-06.