How to plan and deliver lung cancer reirradiation: A consensus approach from the ESTRO reirradiation and lung focus groups and ReCOG.

Lung reirradiation is seeing increased use, yet the evidence base guiding its practice remains limited despite significant technological advances. This paper provides a consensus approach addressing the technical factors underpinning clinical decision-making. It aims to answer the central question: how can clinical teams implement a safe, reproducible, and technically robust workflow for high-dose lung reirradiation? The recommendations are developed by an expert panel of radiation oncologists, medical physicists, and radiation therapists (RTT) from 14 European, American, and Canadian centres, synthesizing a broad range of clinical perspectives. The scope of this work/manuscript is to provide a structured, practical workflow applicable across diverse clinical settings. Using a clinical case, the manuscript demonstrates key conceptual principles, such as the rationale for advanced dose accumulation and the impact of anatomical changes during treatment, with clear, stepwise guidance to support consistent implementation and informed clinical judgement. Key recommended steps include retrieval of prior treatment data; consideration of prior positioning and motion management; and equieffective dose accumulation using deformable image registration or organ-at-risk (OAR)-focused rigid registration. Treatment planning should explicitly incorporate prior dose while balancing target coverage against OAR limits. Daily online volumetric image guidance is central to evaluating both bony and soft-tissue anatomy, enabling setup adjustments to protect critical structures approaching tolerance. Clear documentation and multidisciplinary communication are integral throughout. This consensus approach is intended to support both centres that aim to establish reirradiation practice and experienced teams seeking to harmonize best practices.