SU‐E‐T‐18: A Comparison of Planning Techniques for Bilateral Reconstructed Chest Wall Patients Undergoing Whole Breast Irradiation

Abstract

Purpose:As we continuously see more bilateral reconstructed chest wall cases, new challenges are being presented to deliver left‐sided breast irradiation. We herein compare three Deep Inspiration Breath Hold (DIBH) planning techniques (tangents, VMAT, and IMRT) and two free breathing techniques (VMAT and IMRT).Methods:Three left‐sided chest wall patients with bilateral implants were studied. Tangents, VMAT, and IMRT plans were created for DIBH scans. VMAT and IMRT plans were created for free breathing scans. All plans were normalized so that 95% of the prescription dose was delivered to 95% of the planning target volume (PTV). The maximum point dose was constrained to less than 120% of the prescription dose. Since the success of DIBH delivery largely depends on patient's ability to perform consistent breath hold during beam on time, smaller number of Monitor Units (MU) is in general desired. For each patient, the following information was collected to compare the planning techniques: heart mean dose, left and right lung V20 Gy, contra‐lateral (right) breast mean dose, cord max dose, and MU.Results:The average heart mean dose over all patients are 1561, 692, 985, 1245, and 1121 cGy, for DIBH tangents, VMAT, IMRT, free breathing VMAT and IMRT, respectively. For left lung V20 are 60%, 28%, 26%, 30%, and 29%. For contra‐lateral breast mean dose are 244, 687, 616, 783, 438 cGy. MU are 253, 853, 2048, 1035, and 1874 MUs.Conclusion:In the setting of bilateral chest wall reconstruction, opposed tangent beams cannot consistently achieve desired heart and left lung sparing. DIBH consistently achieves better healthy tissue sparing. VMAT appears to be preferential to IMRT for planning and delivering radiation to patients with bilaterally reconstructed chest walls being treated with DIBH.