Intensity-modulated radiotherapy using two static ports of tomotherapy for breast cancer after conservative surgery: Dosimetric comparison with other treatment methods and 3-year clinical results

This study investigated the differences in dose-volume parameters for the breast and normal tissues during tomodirect tm (td) intensity-modulated radiation therapy (imrt),td-3d conformal radiotherapy (3dcrt) and 3dcrt plans,all using two beams,and analyzed treatment outcomes of two-beam td-imrt for breast cancer after breast-conserving surgery. between august 2011 and january 2015,152 patients were treated using two-beam td-imrt with 50 gy/25 fractions. among them,20 patients with left-sided breast cancer were randomly chosen,and two-beam td-imrt,td-3dcrt and 3dcrt plans were created for each patient. the homogeneity and conformity indices and various dose-volume parameters for the planning target volume and oars were evaluated. clinical outcomes were evaluated at 3 years. toxicities were evaluated using the common terminology criteria for adverse events version 4.0. td-imrt and td-3dcrt showed better whole-breast coverage than 3dcrt (p < 0.001). most of the mean values of dosimetric endpoints for oars were better in td-imrt than in td-3dcrt and 3dcrt. overall survival rates were 97.7% and local control rates were 99.1% at 3 years. regional control and distant metastasis control rates at 3 years were 98.6% and 96.8%,respectively. twenty-four of the 152 patients had grade 2 or higher acute radiation dermatitis. four patients (4/146 = 2.7%) had grade 2 radiation pneumonitis. there were no late adverse events of grade 2 or higher. two-beam td-imrt appeared to yield better dose distribution for whole-breast external-beam radiation therapy than td-3dcrt and two-beam 3dcrt. the treatment appeared to provide low skin toxicity and acceptable tumor control. © 2017 the author. published by oxford university press on behalf of the japan radiation research society and japanese society for radiation oncology.