Prone left-sided whole-breast irradiation: Significant heart dose reduction using end-inspiratory versus end-expiratory gating

Abstract Purpose To quantify the influence on heart dose metrics of prone left-sided whole-breast irradiation in an end-inspiratory phase (Pr IN ) versus an end-expiratory phase (Pr EX ). Patients and methods Twenty patients underwent CT-simulation in Pr IN and Pr EX . Dynamic intensity-modulated radiotherapy was planned for whole-breast irradiation with a median prescription dose of 40.05 Gy in 15 fractions and maximal sparing of the organs at risk. Dose–volume parameters were analyzed for heart, left anterior descending coronary artery, ipsilateral lung and both breasts. Results Pr IN consistently reduced ( P EX . Population averages for maximum and mean heart dose were 6.2 Gy and 1.3 Gy for Pr IN versus 21.4 Gy and 2.5 Gy for Pr EX , respectively. Moreover, a maximum heart dose less than 10 Gy was achieved in 80% of patients for Pr IN . Target dose distribution, ipsilateral lung and contralateral breast sparing by radiation dose were similar for both procedures. Conclusions Inspiratory gating consistently reduced heart dose metrics pointing to a possible benefit of breathing-adapted radiotherapy for prone left-sided whole-breast irradiation.