Radiation therapy with elective lymph node irradiation for breast cancer: dosimetric study and impact on cardiovascular risk and second neoplasms

Adriana Aranha Pereira Machado, Polyana Mendes Maia, Cassio de Queiroz Tannous, Antônio Cássio Assis Pellizzon, Fabiana Baroni Makdissi, Ricardo César Fogaroli, Michael Jenwei Chen, Maria Letícia Gobo Silva, Douglas Guedes de Castro, Guilherme Rocha Melo Gondim

The aim of this study was to perform dosimetric analysis of radiotherapy (RT) plans with or without elective nodal irradiation (ENI) and estimate whether the increase in mean doses (MDs) in the heart and lungs with ENI may lead to late side effects that may surpass the benefits of treatment. The dosimetric analysis of 30 treatment plans was done with or without ENI. The planning and dose-volume histograms were analyzed, and the impact on the mortality of cardiovascular and lung cancer was estimated based on the correlation of the dosimetric data with data from population studies. RT with ENI increased the doses in the lungs and heterogeneity in the plans compared to breast-exclusive RT. When the increase in MDs is correlated with the increase of late side-effect risks, the most important effect of ENI is the increased risk of lung cancer, especially in patients who smoke (average increase in absolute risk=1.38%). The increase in the absolute risk of cardiovascular diseases was below 0.1% in the all the situations analyzed. ENI increases the heterogeneity and the doses at the lungs. When recommending ENI, the risks and benefits must be taken into account, considering the oncology factors and the plan of each patient. Special attention must be given to patients who smoke as ENI may lead to a significant increase in MD in the lung and the increased risk of radiation-induced lung cancer may surpass the benefits from this treatment.