Purpose: To evaluate the radiation dose of the left anterior descending coronary artery (LADA) for the patients treated with deep inspiration breath-hold (DIBH) technique. In routine clinical treatment planning for the left breast cancer patients, the dose-volume histogram (DVH) analysis of the LADA is not commonly evaluated because its dose constraint information is not enough to analyze clinical toxicities in terms of a critical volume with total dose in number of fractions.
Methods: Ten left breast patients with various tumor sizes and positions previously treated with field-in-field tangential beam and DIBH were randomly selected. The LADAs were manually contoured. DIBH based on 4DCT (4-dimensional computer tomography) was used for each patient to minimize the heart irradiation. For treatment planning, the prescription dose was 42.6 Gy in 16 fractions. Organs at risk (OAR) included LADA, heart, lumpectomy cavity and lungs.
Results: The volume of LADA from this study was measured to be 0.25±0.07 cm³. There was not a difference to the sizes, but the positions were changed by the patients’ anatomic structure. The dose to LADA were affected by these. The mean, minimum and maximum dose of LADA were 5.37±1.94, 2.03±0.87, and 13.15±8.20, while the mean, minimum and maximum dose of heart were 1.31±0.36, 0.13±0.04, and 18.16±11.99, respectively. The mean dose ratio of LADA to heart was 4.1.
Conclusion: Our evaluation of the LADA dose demonstrated lower mean dose and standard deviation than other institutions. More clinical evaluations are required from this study in terms of the discrepancy of LADA delineation among the planners and inclusion of the dose effect from electron boost.