Table 1.

The extra organs at risk retrospective added for the purposes of analysing the study

Organ at risk	Mode and nature of creation
Normal lung tissue	Both lungs including inflated and collapsed lungs were contoured automatically using RayStation’s MBS functionality, excluding the GTV to be more representative of normal lung tissue.
Spinal cord	Automatically contoured using MBS and based on the bony limits of the spinal canal. The structure included at least 5 cm superior and inferior to the extent of the PTV.
Oesophagus	Contoured using mediastinal windowing on CT scan, 5 cm superior and inferior to the extent of the PTV (gastroesophageal junction determined as the inferior limit if <5 cm).
Heart	Defined including the pericardial sac. The superior aspect was at the level where the pulmonary trunk and pulmonary arteries first seen as separate structures. The inferior aspect was the inferior wall of the left ventricle.

GTV, gross tumour volume; MBS, model-based segmentation; PTV, planning target volume.