Dose-effect analysis of late dental adverse effects following radiation therapy in survivors of paediatric head and neck rhabdomyosarcoma

Introduction Paediatric head and neck rhabdomyosarcomas (HNRMS) often require radiotherapy, causing dental complications during critical development. Limited literature suggests dose-dependent risks, but clear thresholds for late dental adverse effects are lacking. This study aims to characterize dose effects on developing dentition in paediatric HNRMS patients to identify dose-response relationships informing evidence-based treatment planning.Materials and methods Orthopantomograms from survivors of HNRMS were evaluated using the validated DENTALE scoring system. Radiation doses from brachytherapy, external beam radiation with protons and photons to deciduous teeth were retrieved from treatment plans and converted to EQD2 (α/β = 3 Gy). Dose-response relationships were modelled per tooth using binary logistic regression in Mplus (COMPLEX option for within-patient dependency; model fit assessed by ROC analysis).Results Among 34 survivors (median age at diagnosis 5.6 years), 27 (79.4 %) exhibited late dental AE. Of 919 assessable permanent teeth, 242 (26.3 %) showed abnormalities. Increasing radiation dose was consistently associated with higher AE probability. The dose corresponding to 50 % predicted probability of any dental AE was 23 Gy(EQD2). Structure-specific thresholds were higher for crowns (68 Gy) and eruption disturbances (52 Gy(EQD2)), and lower for roots (24 Gy(EQD2)) and crown-root ratio abnormalities (36 Gy(EQD2)).Conclusion This study demonstrates dose-effect relationships for radiation exposure of developing dentition, with clinically relevant structure-specific thresholds. Teeth receiving no radiation still show developmental abnormalities, likely due to chemotherapy. These findings support incorporating dentition as organ at risk and dose constraints into paediatric head-and-neck radiotherapy planning to reduce dental morbidity.