[Benefits of breathing-adapted radiation therapy for breast cancer]

The purpose of this study was to compare free-breathing radiotherapy, end-expiration gating and end-inspiration gating for left breast cancer, with respect to the target volume coverage and dose to organs at risk.

Sixteen patients underwent 3D and 4D simulation CT. For each patient, five dosimetric plans were compared: free breathing, end-inspiration gating, end-expiration gating, and two optimised plans with a 3mm reduction of the posterior field edge to create optimised end-inspiration and end-expiration plans. Dose-volume parameters, including planning target volume coverage and dose to lung, heart and left anterior descending coronary artery were analysed.

Planning target volume coverage was adequate and similar in the five dosimetric plans (P=0.49). Significant advantage was found for end-inspiration gating in sparing the ipsilateral lung, heart and left anterior descending coronary artery compared to free-breathing 3D radiotherapy. Optimised end-inspiration was even more favourable than end-inspiration gating (P<0.05), with less dose delivered to the ipsilateral lung, heart and left anterior descending coronary artery. When compared to end-expiration gating, end-inspiration gating dosimetric outcomes were similar regarding lung and left anterior descending coronary artery doses, but the heart dose was inferior on the end-inspiration gating compared to end-expiration gating.

Breathing-adapted radiation therapy allowed for dose reduction to organs at risk (left lung, heart and left anterior descending coronary artery), while keeping the same planning target volume coverage. Therefore it can be considered as an interesting option for left breast cancer radiation treatment.