'SOURCE - LUNG' Stereotactic Ablative Radiation Therapy Of UltRaCEntral LUNG Tumours (SOURCE Lung)

This study is a phase II non-randomised, multi-centre, single arm trial of image-guided (IG)-SABR for patients with high-risk centrally located T1-T4 lung tumours (NSCLC) or a single pulmonary oligometastatic lesions. Treatment will consist of IG-SABR using a total of 8 fractions of 7.5 Gy per fraction adhering to organ at risk dose-volume histogram constraints allowing a minimum dose coverage of 75% to 95% of the planning target volume (PTV) coverage, and a minimum dose of 87% to 99% of the gross tumour volume (GTV), using dose intensity modulation. The primary aim of the study is to determine the safety of the 8 x 7.5 Gy treatment regimen on the basis of the rate of ≥ Grade 3 treatment related toxicity using NCI CTCAE V5, in patients with medically inoperable early stage, ultracentrally located lung tumours. This is defined by central tumours which are not fulfilling the conservative hybrid DVCs of the LungTech (Adebahr et al., 2015), RTOG 0813 (Bezjak et al., 2015) studies and current UK consortium guidelines with full dose coverage, but which subsequently meet SOURCE DVC's with potentially reduced dose coverage. To remain in line with international practice, the SOURCE Lung protocol was amended to reduce near maximum dose constraints to 0.1cc for OARs (Diez et al. 2022). Toxicities occurring between start of treatment and one-year from the end of treatment, which are possibly, probably or definitely related to radiotherapy will be assessed. A total of 60 evaluable patients will be required for the study. The sample size was calculated using continuous monitoring for toxicity, up to one year post RT, using a Pocock-type boundary. Accrual will be halted if excessive numbers of ≥ Grade 3 TxR-AEs are seen. The regime will not be considered to be safe if \>25% of evaluable patients experience a ≥ Grade 3 treatment-related adverse event (TxR-AE) by the end of 1-year post-RT. This study will be considered adequately safe if ≤ 25% of evaluable patients experience ≥ Grade 3 TxR-AE by the end of 1 year post-RT. The enrolment period is expected to be 6 years. Toxicity assessments will be carried out weekly during radiotherapy (RT), at 2, 4 and 8-weeks post-treatment and at 3, 6, 9, 12, 18, 24 months post treatment and annually thereafter to 5 years post treatment. Translational Sub-Study 1 (Raman spectroscopic analysis) - Primary aim is to undertake biomarker discovery using label-free Raman spectroscopy coupled with multivariate statistical methods to identify spectral biomarkers that could: 1. Predict response based on individual radiation sensitivity 2. Monitor response based on individual radiation sensitivity Translational Sub-Study 2 (Proteomic analysis) - Primary aim is to use proteomic analysis of sequential blood samples before, during and after treatment to detect changes in protein expression profiles that may predict outcome and identify prognostic biochemical markers of early toxicity.