Robust Treatment Planning in Intrafraction Motion Using TomoDirect™ Intensity-modulated Radiotherapy for Breast Cancer.

Background/aim To evaluate the robustness of radiotherapy treatment planning optimization for respiratory-moving breast cancer using fixed-angle beams planning TomoDirect™ intensity-modulated radiotherapy (IMRT). Materials and methods A minimax optimisation algorithm was applied to 10 breast cancer patients. Two sets of treatment plans with or without robust techniques were prepared considering anterior-posterior and head-tail movements due to respiration. Parameters were compared between treatment plans: 95% planned target volume (PTV) dose, conformal index and homogeneity index (HI), and organs at risk (OAR) parameters including the lung volume receiving 20 Gy or more (V20) and 5 Gy (V5). Results Robust planning significantly improved parameters of 95% PTV dose and HI, without deteriorating V20 or V5 in the anterior-posterior movement, while it slightly improved 95% PTV and slightly deteriorated V20 in the head-tail movement. Conclusion Robust treatment planning improves coverage of targets moving because of respiration in the treatment of breast cancer using TomoDirect; however, normal lung doses should be cautiously evaluated on a case-by-case basis.