Speaker
Description
The thyroid gland is an organ at risk (OAR) during head-and-neck radiotherapy (RT) due to its proximity to the treatment field. Ionising radiation can damage thyroid tissue, disrupt hormonal regulation by the hypothalamus-pituitary-thyroid (HPT) axis, and lead to endocrine dysfunction. Clinical studies report that 40-50% of patients develop hypothyroidism as a late RT-induced toxicity \cite{rooney2023}. In nasopharyngeal carcinoma (NPC) patients, hypothyroidism peaks ~24 months post-RT, coinciding with a reduction of ~40% in thyroid volume that subsequently stabilises \cite{lin2018}.
This work presents a mechanistic model of ordinary differential equations (ODEs) to simulate RT-induced changes in thyroid volume and T4-TSH dynamics. Thyroid volume reduction is modelled as a dose-dependent fraction of the initial volume derived from the radiobiological linear-quadratic (LQ) formalism. The HPT feedback loop is described using Michaelis-Menten kinetics, with T4 production expressed as a function of thyroid volume \cite{pandiyan2014}. Model parameters were calibrated using longitudinal clinical data from NPC patients \cite{lin2018}.
The model reproduces observed thyroid volume reduction and long-term T4-TSH clinical levels. It provides a baseline for developing a predictive tool to estimate patient-specific risk of RT-induced hypothyroidism. Future work will focus on validating the model and evaluating its predictive performance using individualised patient data.
Bibliography
@article{rooney2023,
author = {Michael K. Rooney and Lauren M. Andring and Kelsey L. Corrigan and Vincent Bernard and Tyler D. Williamson and Clifton D. Fuller and Adam S. Garden and Brandon Gunn and Anna Lee and Amy C. Moreno and William H. Morrison and Jack Phan and David I. Rosenthal and Michael Spiotto and Steven J. Frank},
journal = {Cancers},
title = {Hypothyroidism following radiotherapy for head and neck cancer: A systematic review of the literature and opportunities to improve the therapeutic ratio},
year = {2023},
pages = {4321},
volume = {15},
doi = {10.3390/cancers15174321}
}
@article{lin2018,
author = {Zhixiong Lin and Zhining Yang and Binghui He and Dangdang Wang and Xiaoyin Gao and Shing-yau Tam and Vincent Wing Cheung Wu},
journal = {PLoS ONE},
title = {Pattern of radiation-induced thyroid gland changes in nasopharyngeal carcinoma patients in 48 months after radiotherapy},
year = {2018},
pages = {e0200310},
volume = {13},
number = {7},
doi = {10.1371/journal.pone.0200310}
}
@article{pandiyan2014,
author = {Balamurugan Pandiyan and Stephen J. Merrill and Salvatore Benvenga},
journal = {Mathematical medicine and biology},
title = {A patient-specific model of the negative-feedback control of the hypothalamus-pituitary-thyroid {(HPT)} axis in autoimmune ({H}ashimoto's) thyroiditis},
year = {2014},
pages = {226--58},
volume = {31},
doi = {10.1093/imammb/dqt005}
}
