Deep Inspiration Breath Hold Technique for Right Breast Irradiation with Supraclavicular and Internal Mammary Lymph Nodes

Abstract

To reduce the volume of the ipsilateral lung included in the radiation fields for right breast cancer patients receiving radiation to the breast/chest wall and to the supraclavicular and internal mammary lymph nodes (LN). Based on available literature, it is accepted practice to keep the ipsilateral mean lung dose (MLD) below 15 Gy and the V20 to 20% and when internal mammary LN are included to 30% in order to minimize the risk of radiation pneumonitis. Deep inspiration breath hold (DIBH) increases the lung volume and might help in reducing the ipsilateral lung doses when irradiating the nodes. Nine right breast cancer patients were CT simulated twice, first while free breathing (FB) and then simulated using DIBH technique. All nine patients were contoured on both CT scans for the right and left lungs, heart, breast PTV, tumor bed and tumor bed PTV (for patients suitable to receive simultaneous integrated boost), supraclavicular and internal mammary lymph nodes, according to the ESTRO contouring atlas. 3D plans were created for both FB and DIBH scans. We attempted to keep the ipsilateral lung V20 and the MLD as low as possible without compromising breast and node coverage. For all patients the coverage of the breast PTV was kept identical. The MLD was 15.4±3.2 Gy and 11.3±2.8 Gy for the FB and the DIBH plans, respectively. The V20 for the ipsilateral lung was 30%±7 for the FB plans and 20.9%±6.7 for the DIBH plans. For five patients the ipsilateral lung V20 values for the FB plans were above 30% of the ipsilateral lung volume, which is higher than we accept clinically. With DIBH technique we were able to keep the values below 30%. For those patients who had a V20 value of less than 30%, DIBH still reduced this value from an average of 23.9%±2.6 to 15.8%±3.4 of the ipsilateral lung volume. For patients receiving radiotherapy to the right breast with supraclavicular and internal mammary lymph nodes an additional simulation using the DIBH technique should be considered, so as to spare as much dose as possible to the ipsilateral lung.