Lung and Liver Stereotactic Body Radiation Therapy During Mechanically Assisted Deep Inspiration Breath-Holds: A Prospective Feasibility Trial

Abstract

PurposeRadiation therapy of tumours subject to breathing-related motion during breath-holds (BH) has the potential to substantially reduce the irradiated volume. Mechanically-assisted and non-invasive ventilation (MANIV) could ensure the target repositioning accuracy during each BH while facilitating treatment feasibility through oxygen supplementation and a perfectly replicated mechanical support. However, there is currently no clinical evidence substantiating the use of MANIV-induced BH for moving tumours. The aim of this work was therefore to evaluate the technique performances under real treatment conditions. Methods and MaterialsPatients eligible for lung or liver stereotactic body radiotherapy were prospectively included in a single-arm trial. The primary endpoint corresponded to the treatment feasibility with MANIV. Secondary outcomes comprised intrafraction geometrical uncertainties extracted from real-time imaging, tolerance to BH and treatment time. ResultsTreatment was successfully delivered in 92.9% (13/14) of patients: one patient with a liver tumour was excluded due to a mechanically-induced gastric insufflation displacing the liver cranially by more than 1 cm. In the Left-right/Anteroposterior/Craniocaudal directions, the recalculated safety margins based on intrafraction positional data were 4.6 mm / 5.1 mm / 5.6 mm and 4.7 mm / 7.3 mm / 5.9 mm for lung and liver lesions, respectively. Compared to the free-breathing internal target volume and mid-position approaches, the average reduction in the planning target volume with MANIV reached -47.2±15.3 %, p<0.001 and -29.4±19.2 %, p=0.007 for intra-thoracic tumours and -23.3±12.4 %, p<0.001 and -9.3±15.3 %, p=0.073 for upper abdominal tumours, respectively. For one liver lesion, large caudal drifts of occasionally more than one centimetre were measured. The total slot time was 53.1 ± 10.6 minutes with a BH comfort level of 80.1±10.6%. ConclusionsMANIV enables high treatment feasibility within a non-selected population. Accurate intrafraction tumour repositioning is achieved for lung tumours. Due to occasional intra-BH caudal drifts, pre-treatment assessment of BH stability for liver lesions is however recommended.