The influence of brachytherapy on tooth development: a longitudinal study of pediatric head and neck tumor survivors

Abstract Background Interstitial brachytherapy is an effective and organ-preserving radiotherapeutic modality for pediatric and adolescent patients with head and neck tumors, offering favorable outcomes with minimal impact on surrounding normal tissues. However, the long-term effects of brachytherapy on dental development in young patients remain underexplored, despite clinical observations of tooth anomalies in tumor survivors. This study aimed to provide longitudinal outcomes of tooth developmental anomalies in pediatric and adolescent tumor survivors who underwent head and neck interstitial brachytherapy and to investigate the relevant factors. Methods The longitudinal panoramic radiographs of the patients at different ages before brachytherapy and during follow-up were evaluated. A modified Demirjian staging technique was used to allocate a developmental stage for each tooth, and the defect index classification criteria were applied to describe the severity of tooth damage. Logistic regression analysis was performed to identify factors associated with long-term dental abnormalities. Results A total of 210 developing permanent teeth from seven patients were included and evaluated. There were 31 teeth (14.76%) that exhibited developmental anomalies. The incidence and severity of tooth developmental abnormalities after brachytherapy were jointly determined by the radiation dose received by a given tooth and its developmental stage at the time of treatment. Multivariable analysis indicated that D2cc had the largest effect size (OR 1.029, 95% CI 1.017–1.042) and the most significant statistical association (P = 0.002). When D2cc was 0–10 Gy, the incidence of tooth developmental abnormalities was 1.90%; and when D2cc>100 Gy, the incidence reached 85.7%. The maxillary region with implanted radioactive seeds had a significantly higher risk of dental abnormalities compared to other regions. Conclusion This study suggests that interstitial brachytherapy may contribute to dental developmental alterations in pediatric and adolescent patients, with severity potentially influenced by radiation dose and tooth developmental stage. D2cc appeared to be the most informative dose-volume parameter, with lower risks observed at < 10 Gy and higher risks at > 100 Gy. Although limited by sample size and retrospective design, these findings underscore the importance of considering developing dentition when planning individualized radiotherapy for young patients.