Evaluation of robustness of optimization methods in breast intensity-modulated radiation therapy using TomoTherapy

Abstract

Introduction: Intensity-modulated radiation therapy (IMRT) has become a popular choice for breast cancer treatment. We aimed to evaluate and compare the robustness of each optimization method used for breast IMRT using TomoTherapy.Methods: A retrospective analysis was performed on 10 patients with left breast cancer. For each optimization method (clipping, virtual bolus, and skin flash), a corresponding 50 Gy/25 fr plan was created in the helical and direct TomoTherapy modes. The dose-volume histogram parameters were compared after shifting the patients anteriorly and posteriorly. Results: In the helical mode, when the patient was not shifted, the median D1cc (minimum dose delivered to 1 cc of the organ volume) for breast skin for the clipping and virtual bolus plans were 52.2 (interquartile range: 51.9–52.6) and 50.4 (50.1–50.8) Gy, respectively. After an anterior shift, the D1cc of the breast skin for the clipping and virtual bolus plans was 56.0 (55.6–56.8) and 50.9 (50.5–51.3) Gy, respectively. When the direct mode was used without shifting the patient, the D1cc of the breast skin for the clipping, virtual bolus, and skin flash plans were 52.6 (51.9–53.1), 53.4 (52.6–53.9), and 52.3 (51.7–53.0) Gy, respectively. After shifting anteriorly, D1cc of the breast skin for the clipping, virtual bolus, and skin flash plans was 55.6 (54.1–56.4), 52.4 (52.0–53.0), and 53.6 (52.6–54.6) Gy, respectively. Conclusions: The clipping method is not sufficient for breast IMRT. The virtual bolus and skin flash methods were more effective optimization methods according to our analyses.