ESTRO clinical practice guideline on high-dose thoracic reirradiation for non-small cell lung cancer

Purpose: High-dose thoracic reirradiation is increasingly used in clinical practice for patients with non-small cell lung cancer (NSCLC) in a variety of clinical scenarios ranging from locoregional recurrence to selected metastatic settings. The treatment goals of thoracic reirradiation include durable local control, symptom palliation, and potential cure. Despite growing clinical adoption, high-quality randomised evidence guiding patient selection, treatment delivery, and integration with systemic therapy remains limited. This ESTRO- clinical practice guideline aims to provide expert consensus recommendations for high-dose thoracic reirradiation in NSCLC based on the available literature and structured expert agreement. Materials and Methods: The guideline was developed by an international, interdisciplinary panel of experts in thoracic radiation oncology and reirradiation, including specialists in radiation oncology, clinical oncology, and medical physics from Europe and North America. A structured modified Delphi consensus process was used to derive and refine recommendations and statements addressing predefined key clinical questions covering patient selection, diagnostic workup, target definition, dose and fractionation, treatment planning and delivery, cumulative dose assessment, combination with systemic therapy, and follow-up. Results: A total of 42 consensus recommendations and statements were derived across eight key questions. Recommendations emphasise careful patient selection, comprehensive staging, precise target delineation integrating prior treatment data, and individualized dose and fractionation balancing tumour control with cumulative organ at risk constraints. Highly conformal image-guided techniques and structured cumulative dose assessment were considered essential for safe delivery. Guidance on combining reirradiation with systemic therapy remains conditional due to limited evidence, and standardised follow-up strategies were proposed to monitor side effects and disease control. Conclusions: This ESTRO guideline provides consensus-based recommendations to inform clinical practice for high-dose thoracic reirradiation in NSCLC and is intended to complement existing consensus documents addressing technical, methodological, and workflow aspects of reirradiation. In the absence of robust prospective data, these recommendations support multidisciplinary decision-making while highlighting priorities for future clinical research.