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

Purpose: 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. Materials and methods: Twelve patients were scheduled for radical radiotherapy: five for SRT and seven for 3DCRT. 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). Results: 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 ≥20 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. Conclusion 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.