Estimating cardiac, lungs and right breast doses from conventional left breast cancer radiotherapy

Background: Adjuvant radiotherapy has been given to many women with breast cancer for more than 50 years and it is currently recommended for a substantial proportion of such women. Long-term follow-up of these women has, however, revealed that some past radiotherapy techniques led to cardiac and pulmonary toxicity, because of unwanted irradiation of the cardiac structures and lungs by using traditional 2D techniques. Most of the breast cancer patients in our center traditionally treated with 2D technique and cobalt 60 machine up to 3 years ago. Therefore we present a study on cardiac and pulmonary dose-volume data of conventional 2D tangential breast irradiation achieved by three-dimensional conformal tangential irradiation. The result of this study may be beneficial to guide the radiation oncologists to improve treatment outcome by decreasing radiation toxicities in normal tissues. Material and Methods: Twenty consecutive patients with left-sided breast cancer who were irradiated with 2D- conventional tangential beams, entered to this study. For each patient (CT)-based three-dimensional treatment planning has been used to reconstruct conventional RT regimens. Then images were transferred to treatment planning system, then Contralateral breast, both lungs and heart were contoured after reconstruction of tangential fields by considering radio opaque markers located on field borders. Dose-volume histograms (DVH) for the heart, right breast and both lungs were calculated. Results: For individual women in the study, there was a wide range of cardiac doses of between 4.52 and 19.17Gy and between 9.86 and 24.75Gy mean left lung dose. Conclusion: We strongly advise 3D treatment planning or utilizing shielding system and techniques such as breath holding to reduce the dose irradiated to vital organs in 2D left breast cancer radiotherapy.