The heart's conducting system as a new critical organ in breast cancer radiotherapy

Modern methods of radiotherapy contribute to increasing the life expectancy of patients with breast cancer, but regardless of the choice of treatment methods, the risk of cardiac complications during therapy and in the long term remains. The severity of cardiotoxicity directly depends on the dose of ionizing radiation that falls on the myocardium, the conducting system of the heart and blood vessels (LADCA, right coronary artery). In this regard we consider the reduction of the radiation dose that falls on the above structures, while maintaining an adequate dose distribution in the planned volume of the target. The distribution of radiation dose in the atrioventricular node, sinoauricular node, and bundle of His was studied in 24 patients, 18 of whom received organ- preserving surgical treatment for breast cancer, and 6 patients underwent mastectomy. Our research has shown that not always the most modern technologies (VMAT, IMRT) for breast irradiation are optimal, especially for patients with cardiovascular diseases, since when they are used, the conducting system of the heart has a large dose load, mainly due to the effect of low dose bath. The study revealed that dose of ionizing radiation depends on the size of the target and found that SA- node receives larger radiation dose during right-sided irradiation, while bundle of His and AV-node receives larger radiation dose in left-sided irradiation.