Introduction: The purpose of the study was to determine if multi-field inverse-planned intensity-modulated radiation therapy (IMRT) improves on the sparing of organs at risk (heart, lungs and contralateral breast) when compared with field-in-field forward-planned RT (FiF).
Methods: The planning CT scans of 10 women with left-sided breast cancer previously treated with whole-breast RT on an inclined breast board with both arms supported above the head were retrieved. The whole breast planning target volume (PTV) was defined by clinical mark-up and contoured on all relevant CT slices as were the organs at risk. For each patient, three plans were generated using FiF, five- and nine-field inverse-planned IMRT, all to a total dose of 50 Gy to the whole breast. Mean and maximum doses to the organs at risk and the homogeneity index (HI) of the whole-breast PTV were compared.
Results: The mean heart dose for the FiF plans was 2.63 Gy compared with 4.04 Gy for the five-field and 4.30 Gy for the nine-field IMRT plans, with no significant differences in the HI of the whole-breast PTV in all plans. The FiF plans resulted in a mean contralateral breast dose of 0.58 Gy compared with 0.70 and 2.08 Gy for the five- and nine-field IMRT plans, respectively.
Conclusions: FiF resulted in a lower mean heart and contralateral breast dose with comparable HI of the whole-breast PTV in comparison with inverse-planned IMRT using five or nine fields.
© 2011 The Authors. Journal of Medical Imaging and Radiation Oncology © 2011 The Royal Australian and New Zealand College of Radiologists.