Deep inspiration breath hold in left sided tangential breast radiotherapy: Degree of lung inflation needed to compansate for cardiac motion

Abstract

Background: To determine the degree of lung inflation sufficient to compensate for cardiac motion in patients receiving standard tangential left-breast radiotherapy during deep inspiration breath hold (DIBH). Materials and Methods: Computed tomography (CT) scans were performed in 20 patients with left-sided early breast cancer during free breathing (FB) and DIBH. Standard tangential field plans were generated in both CT sets. Doses to the organs at risk were assessed. The margin between the left anterior descending artery (LAD) and posterior field edge was measured from the closest point. Results: The DIBH plans showed equal coverage of the breasts, so it was possible to obtain lower cardiac doses with DIBH. The median increase in the left-lung volume with DIBH was 53% (range 12.6% -108%). A LAD safety distance ≥ 5mm from field edges was not obtained in any of the patients during FB, whereas in 60% of the patients during DIBH the safety distance was obtained. The lung inflation rate and cardiac safety distance were strongly correlated. The mean distance between the LAD and tangential field posterior edge increased significantly from 0.23 cm to 0.64 cm (p=0.041) in the patients who inflated their ipsilateral lung > 1.5 times. Conclusion: Lung inflation of ≥50% compensated for cardiac motion during treatment using DIBH. The lung inflation capacity should be considered in choosing the irradiation technique in left-sided breast cancer patients.