Avaliação da dose de radiação absorvida em diferentes estruturas cardíacas: comparação de técnicas de tratamento radioterápico em pacientes com câncer de mama

Abstract

Breast cancer is the most common type among women. Due to the anatomical position of the breast, radiotherapy can cause side effects to adjacent normal tissues, especially to the heart. Some recent studies already associate 3D-CRT and IMRT techniques with late cardiac toxicity. The objective of this study is to evaluate the dose distribution received by the breast and organs of risk, with emphasis on individual heart structures, for 2 different techniques of radiotherapy treatment (Field-in-Field and 3D-CRT) in patients undergoing conservative surgery of the left breast through a comparison between the 2 techniques. A 64-channel multislice CT image was done synchronized to the electrocardiogram after injecting iodinated contrast medium in 18 patients. A radio-oncologist and a cardiologist delineated the contours of target volumes and substructures of the heart: pulmonary trunk, heart, right and left ventricles, right and left atria, left anterior descending artery, right coronary artery, circumflex artery and aorta. In a treatment planning system, plans were performed with 3D-CRT (3D) and Field-in-field (FiF) techniques for each patient. Analyzing the dose-volume histogram, the volumes for different doses (V2, V5, V10, V20, V25 and V30) and the mean and maximum doses received by each delineated structure were determined. The means and respective standard deviations were calculated and the statistical analysis (Wilcoxon test) of the results was performed. The study concludes that angiotomography is an effective tool to support the precise delineation of each substructure during the treatment planning process. In addition, the study demonstrated benefits in relation to the dose distribution of the FiF technique when compared to 3D for the radiotherapy treatment of patients with left breast cancer. Almost all of the analyzed structures suffered lower irradiation with the FiF technique in relation to 3D, with all p-values being significant.