Management of Clinical Variability in Radiotherapy Delivery: Explicit Treatment-Delivery Judgment and a Three-Layer Framework.

Radiotherapy delivery is founded on standardization, protocol adherence, and quality assurance to ensure precision, reproducibility, and patient safety. However, clinical variability remains unavoidable because patient anatomy, organ filling, immobilization conditions, physiological status, image quality, and workflow constraints can change across treatment fractions. During daily cone-beam computed tomography (CBCT)-based verification, predefined protocols and tolerance thresholds provide essential safety boundaries but do not always determine the most appropriate action in complex or borderline situations. This discussion paper examines clinical variability in radiotherapy delivery and proposes a three-layer framework for making treatment-delivery judgment explicit and governable, distinguishing a protocol-based safety baseline, a guideline-based consensus domain, and a bounded judgment-based domain. An organizational learning loop is proposed to convert recurrent judgment scenarios into explicit institutional standards through documentation, peer discussion, interdisciplinary review, standard-operating-procedure refinement, audit, and education. The paper also considers how this framework relates to current radiotherapy practice, where radiation therapists operate within institutional and regulatory boundaries that differ across settings. The approach supports governance, patient safety, professional education, and accountability without redefining medical decision-making authority.