Treatment Procedure

Patients were treated with stereotactic body radiation therapy based on the 4D-CT with 3 mm slice thickness taken in free breath mode. Critical structures, including spinal cord, heart, brachial plexus, and oesophagus were outlined, and dose constraints are used according to accepted standards (29) ( Supplementary Table S1 ). Combining the gross target volume (GTVs) (determined by contouring the macroscopic tumour using lung window) in seven respiratory positions without extension, internal target volume (ITV) was generated. Planning target volume (PTV) was produced by the 0.6-cm extension of the ITV. An eighth, average CT reconstruction was also generated and used for dose calculation and optimisation. Forty-two patients were treated with 8 × 7.5 Gy, and three patients were treated with 5 × 12 Gy. We used volumetric modulated arc therapy (VMAT) technique, 6 MV accelerator energy with flattening filter free (FFF) mode and 1,400 MU/min dose rate. We used Varian Eclipse 13.7 planning system (AAA calculation algorithm) and TrueBeam linear accelerator.