An Alternative Option for Reducing Lung Dose for Electron Scar Boost Irradiation in Postmastectomy Breast Cancer Patients With a Thin Chest Wall

Abstract

dose volume histogram (DVH) of CTV and organ at risks (OARs) were compared with the corresponding unperturbed reference plans. Results: For the liver cases, CTV-based optimization is similar to PTVbased optimization methods for both CTV coverage and dose changes in OARs when dealing with beam range and setup uncertainties. Both methods achieve sufficient CTV coverage under the worst-case scenarios. For the lung cases, CTV-based optimization was much more robust to deal with uncertainties than PTV-based optimization. Under the worst-case scenarios, CTV coverage (V100%) was degraded by 40AE18% and 3AE2% for PTV-based and CTV-based optimization method, respectively. Conclusion: Based on a limited patient cohort, CTV-based robustness optimization is much less sensitive to beam range as well as setup uncertainties than PTV-based optimization for lung cases using IMPT. However, in case of liver PTV-based optimization may be sufficient to account for dosimetric and set up uncertainties. This may be due to the fact that lung tumors are surrounded by low density lung tissues, which are more sensitive to the uncertainties in the beam pathway compared to the liver tissues.