Influence of different treatment planning techniques on radiation doses to the heart, left anterior descending coronary artery and left lung in the radiotherapy of left-sided breast cancer patients

Background: Breast-conserving surgery (BCS) followed by radiotherapy (RT) is the standard of care for women with breast cancer. Evidence shows that RT dose to the heart can result in ischemic heart disease. In this study we compared 3 different RT techniques were for heart, left anterior descending coronary artery (LAD) and lung doses in left breast cancer patients after breast-conserving surgery. Materials and Methods: Three different plans were designed for each patient using conventional tangential fields, 6+18 MV combination beams, and field-in-field (FIF) technique. These were compared in terms of doses to the planning target volume (PTV), ipsilateral lung, heart and LAD. Results: Forty left breast cancer patients were included in this study. Mean PTV V95% was 95.74% for conventional, 90.45% for FIF and 87.89% for 6+18 MV combination beams (p<0.05). Mean left lung dose was 11.22 Gy for FIF, 12.25 Gy for 6+18 MV and 12.95 Gy for conventional technique (p<0.05). Mean heart dose was 4.52 Gy for FIF, 4.85 Gy for 6+18 MV and 5.13 Gy for conventional technique (p<0.05), and mean D2% for LAD was 40.06, 43.43 and 45.25 Gy (p<0.01) in FIF, 6+18 MV and conventional techniques, respectively. Conclusion: These results indicated that FIF and 6+18 MV combination techniques significantly reduced the doses received by the heart, LAD and left lung compared to conventional tangential fields, while FIF was superior to 6+18 MV considering the above-mentioned variables. The lower doses to the organs at risk were achieved with a small but statistically significant loss in PTV coverage.