Impact of a breathing-control system on target margins and normal-tissue sparing in the treatment of lung cancer: experience at the radiotherapy unit of Florence University

In lung cancer, a high radiation dose to the target area correlates with better local control but is frequently counterbalanced by a higher risk of lung toxicity. Several methods exist to coordinate respiratory motion in lung radiotherapy. We aimed to investigate the impact of a breathing-control system on irradiated volumes and dosimetric parameters in three-dimensional conformal radiotherapy (3D-CRT) and stereotactic radiotherapy (SRT) treatments. Twelve patients were scheduled for radical radiotherapy: five for SRT and seven for 3D-CRT. For each patient, in addition to the free-breathing computed tomography (CT) scan, four additional sets of CT slices were acquired using the Active Breathing Coordinator device (ABC, Elekta Oncology Systems Ltd., UK). The volumes acquired with the ABC device were significantly smaller than the free-breathing volumes [23 % reduction of planning tumour volume (PTV), p = 0.002]. ABC allowed a reduction of all dosimetric parameters [2.28 % reduction of percentage volume of lung treated to a dose of a parts per thousand yen20 Gy (V20), p = 0.004; 10 % reduction of mean lung dose (MLD), p = 0.009]. Significant differences were found both in SRT and in 3D-CRT, in peripheral and apical lesions. In our experience, ABC has the potential to reduce lung toxicity in the treatment of lung cancer; alternatively, it can allow the prescribed dose to be increased while maintaining the same risk of lung toxicity.