Ventilation Imaging to Improve the Quality of Life for Patients With Lung Cancer Treated With Radiation Therapy

Inclusion Criteria 1. Aged 18 years or older. 2. Eastern Cooperative Oncology Group (ECOG) performance status 0-2. 3. Histologically proven non-small cell lung cancer. 4. Stage 3 as determined using the IASLC (International Association for the Study of Lung Cancer) 8th edition lung cancer staging guidelines. 5. To be treated with curative intent external beam radiotherapy (60 Gy in 30 treatments or 55 Gy in 20 treatments) +/- concurrent chemotherapy and adjuvant PD1/PD-L1 inhibitors. 6. Whole body Positron Emission Tomography (PET) scan within 8 weeks of registration. 7. Pulmonary function tests within 8 weeks of registration. 8. Willingness to give written informed consent. 9. Willingness to comply with the study procedures and visit requirements. 10. Available for follow up for a minimum of 12 months and up to 3 years. Post-inclusion criteria includes the results of a Quality of Life (QoL) assessment and treatment plan assessment, neither of which are known prior to consent. The post-inclusion criteria for the VITaL trial are: 1. Functional Assessment of Cancer Therapy - Lung (FACT-L) Trial Outcome Index (TOI) score of ≥5, the clinically meaningful difference 2. The standard treatment plan shows that at least 16% of volume of the lungs (minus the Gross Tumour Volume (GTV)) will receive more than 20 Gy. This criterion is based on the difference in pneumonitis risk between patients receiving below (\~8%) and above (\~34%) this threshold. The QoL assessment is unlikely to eliminate any patients but is included for patients where no clinically meaningful difference will be possible. The treatment plan assessment may exclude 20% of otherwise eligible patients. Exclusion Criteria: 1. Serious medical comorbidities that may contraindicate curative radiotherapy. 2. Inability to attend full course of radiotherapy or follow-up visits. 3. A current or former diagnosis of interstitial lung disease. 4. Prior history of lung cancer within 5 years. 5. Prior thoracic radiotherapy at any time. 6. Prior surgery for this cancer within a year. 7. Prior chemotherapy for this cancer. 8. Pregnant or lactating women.