Abstract P1-10-14: Higher radiation dose to the heart in left sided breast cancer; anatomy versus dosimetry

Abstract

Abstract Abstract: Background: There is assumption that omitting the internal mammary chain radiotherapy (IMC RT) in patients with breast cancer (BC) will significantly reduce the cardiac exposure for all patients regardless the cardiac anatomy of each patient. Aim: to evaluate the impact of IMC RT on the dose received by the heart and its chambers in patients with favorable versus unfavorable cardiac anatomy. Patients and methods: CT scans were obtained of 20 patients with left-sided BC, 10 with favorable and 10 with unfavorable cardiac anatomy. Three plans were generated for each patient, one treating only the breast with tangents, and one treating the breast and IMC with wide photon tangents, and one treating the breast and IMC to 50Gy with photon tangent fields and a matching medial electron field. Dose volume histograms (DVHs) were generated for the heart and chambers. The equivalent uniform doses (EUDs) were calculated for each DVH, and the mean EUDs for plans with unfavorable and favorable cardiac anatomy were compared using a two-sided two-sample T-test Results: The mean dose received by the heart from plans with tangents plus IMC fields in patients with favorable cardiac anatomy was significantly lower than that received from plans with tangents only or wide tangents in patients with unfavorable anatomy (P < .0001). The average EUD for plans with tangents and IMC fields in the favorable group was 16 Gy (SD = 4.5) as compared to 36 Gy (SD = 3.6) and 37 Gy (SD = 5.1) for plans with tangents only and wide tangents in the unfavorable group, respectively ((P < .0001). The doses to the right ventricle were not significantly different. Conclusions: Ttreatment plans should be individualized based on the cardiac anatomy of each patient. Citation Format: Mohamed Alm El-Din, Andrzej Niemierko, Alphonse Taghian. Higher radiation dose to the heart in left sided breast cancer; anatomy versus dosimetry [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-10-14.