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

PURPOSE

To quantify the influence on heart dose metrics of prone left-sided whole-breast irradiation in an end-inspiratory phase (PrIN) versus an end-expiratory phase (PrEX).

PATIENTS AND METHODS

Twenty patients underwent CT-simulation in PrIN and PrEX. Dynamic intensity-modulated radiotherapy was planned for whole-breast irradiation with a median prescription dose of 40.05Gy 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

PrIN consistently reduced (P<0.001) heart and left anterior descending coronary artery dose metrics compared to PrEX. Population averages for maximum and mean heart dose were 6.2Gy and 1.3Gy for PrIN versus 21.4Gy and 2.5Gy for PrEX, respectively. Moreover, a maximum heart dose less than 10Gy was achieved in 80% of patients for PrIN. 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.