The Generation of thoracic dose constraints based on BED study is a retrospective analysis of the radiotherapy planning data and associated reported toxicity for patients from the IDEAL-CRT trial. IDEALCRT was a phase I/II trial of concurrent chemoradiation with dose escalated radiotherapy in patients with stage II/III non-small cell lung cancer. The Generation of thoracic dose constraints based on BED study will utilise this data to correlate toxicity (Grade 2-5) with dose converted to BED/EQD2 using radiobiological modelling to generate dose constraints in-line with the original objective of the trial. Data will be analysed using the Lyman Kutcher Burman NTCP mode. The Generation of thoracic dose constraints based on BED study aims to generate thoracic dose constraints based on biologically effective dose or equivalent dose in 2Gy fractions to allow a single set of dose constraints to be used for non-standard lung radiotherapy treatment fractionations. The determination of the alpha-beta ratio for lung and oesophagus is an essential part of this project for the radiobiology calculations to accurately convert doses to BED/EQD2.