UCSF

Reirradiation can be considered for some patients with recurrent or second primary head and neck squamous cell carcinoma arising within previously irradiated regions, a clinical scenario associated with few therapeutic options. The increasing use of modern conformal radiotherapy techniques, including intensity-modulated radiotherapy, proton therapy, and stereotactic body radiotherapy, has expanded the feasibility of reirradiation in clinical practice. However, evidence remains heterogeneous, and clinical choices are challenged by substantial variability in patient presentation, previous treatments, and toxicity risk. This international expert consensus statement aims to provide pragmatic guidance across key domains, including patient selection, imaging, target delineation, treatment planning, dose accumulation, and toxicity management. Developed through a structured expert consensus process with formal agreement assessment, this document reflects current expert practice. By offering a shared clinical framework, this consensus seeks to promote more consistent practice, facilitate communication across centres, and support future research efforts in this complex and evolving field.