Dose Mapping and Accumulation for Re-Irradiation of Lung Cancers: Methodological Principles, Uncertainties, Quality Assurance, and Practical Clinical Considerations

Background/Objectives: Thoracic re-irradiation is increasingly considered for recurrent, persistent, or new lung cancers after prior radiation therapy. The central clinical-technical challenge is relating prior and prospective doses across changes in anatomy, breathing state, fractionation, and imaging. Methods: This clinical-technical Perspective synthesizes consensus guidance, technical and the methodological literature, and representative clinical evidence to discuss rigid and deformable registration, dose mapping, biological normalization with EQD2/BED, uncertainty, quality assurance, and practical decision-making in lung re-irradiation. Results: Cumulative dose is an estimate with inherent uncertainty whose clinical value depends on the clinical question, anatomic stability, tissue correspondence, dose-transfer method, biological assumptions, and the consequence of error. Published cumulative dose constraints can provide useful orientation, but they are not universal pass/fail thresholds and should be interpreted together with their original endpoints, assumptions, and accumulation method. Conclusions: A focused, risk-adapted workflow can support more defensible use of cumulative dose in lung re-irradiation. Practical considerations in this article are intended to complement formal consensus guidance, institutional protocols, or patient-specific multidisciplinary judgment.