Assessment Of The Dose To The Heart And The Left Anterior Descending Coronary Artery For The Left Breast Radiotherapy

Radiotherapy for left breast cancer may increase risk of cardiovascular diseases. Exposing the anterior portion of the heart and left anterior descending coronary artery (LAD) to the highest radiation dose depends on individual anatomical location of these structures. The purpose of this work was to assess the radiation doses delivered to the heart and the LAD for the left sided breast cancer patients treated with 3D conformal radiotherapy. Thirty two randomly selected patients referred for adjuvant radiotherapy after conservation surgery for left sided breast cancer were evaluated. The whole heart, the arch of the LAD (LADarch) and the whole LAD were contoured. The radiation doses (Dmax, Dmean) to these three anatomical cardiac structures were evaluated. For all 32 patients, the assessed radiotherapy plans were acceptable based on the dose constraints to critical structures: heart, LADarch. The average mean doses (Dmean) to the heart are well below 5 Gy and 7,3 (range, 3,82 – 17,15 Gy) for the LADarch respectively. For 21,9% of patients, the Dmean to the heart and dose to the LADarch was relatively low while the Dmean to the whole LAD was considerably higher. Conclusion. Evaluation of the mean dose to the heart only could lead to excessive heart irradiation. The results of the study indicate that it is necessary to assess the dose delivered to the whole heart as well as to the whole LAD for evaluation of the left breast irradiation treatment plan. This is very important to minimise the risk of clinically significant cardiac events after left breast radiotherapy.