Multivariate NTCP Model of Hypothyroidism After Intensity-Modulated Radiotherapy for Nasopharyngeal Carcinoma

Abstract

ObjectiveTo evaluate the incidence of hypothyroidism in patients with nasopharyngeal carcinoma after intensity-modulated radiotherapy (IMRT), analyze its correlation with multiple influencing factors such as thyroid exposure dose, thyroid volume, and gender, and construct a multivariate-based normal tissue complication probability (NTCP) model for the occurrence of hypothyroidism after IMRT.Materials and MethodsThe thyroid hormone levels of patients at different points in time before and after radiotherapy were tested, and statistics on the incidence of hypothyroidism after treatment were obtained. The dose-volume data of patients’ thyroids were converted into EQD2 equivalent dose values. The correlation between hypothyroidism after radiotherapy and thyroid exposure dose, thyroid volume, gender, and other factors was analyzed, and an NTCP model was constructed.ResultsA total of 69 patients with nasopharyngeal carcinoma were enrolled in this study. Twelve months after radiotherapy, a total of 24 patients (34.8%) developed hypothyroidism. Univariate analysis and multivariate analysis revealed that the average thyroid dose and thyroid volume are the most important factors affecting hypothyroidism after radiotherapy. The NTCP model constructed based on the average dose and thyroid volume has a good degree of fit.ConclusionThe volume and average dose of the thyroid gland are the key factors affecting the occurrence of hypothyroidism in patients with nasopharyngeal carcinoma after radiotherapy. The NTCP model constructed based on multivariate construction suggests that reducing the average dose of the thyroid to the greatest extent is an effective way to protect thyroid functions.

Early post-treatment 18F-FDG PET/CT for predicting radiation-induced hypothyroidism in head and neck cancer

“…Several clinical parameters, including age, sex, pre-existing thyroid disease, thyroid size, and radiation dose, have been associated with the development of RIHT. A prospective study identified mean radiotherapy dose to the thyroid and pretreatment thyroid volume as potential predictors of RIHT development [ 15 ]; these predictors were validated in subsequent studies on breast cancer and nasopharyngeal carcinoma [ 16 , 17 ], as well as in the present study. Interestingly, in the present study, the AUCs for these predictors were lower (although not significantly) than those for early post-treatment thyroid functioning volume.…”

Evaluation of radiation side effects on thyroid function

“…Head and neck radiation therapy results in significant doses of radiation to the thyroid gland (10-80 Gy) because all or a large part of the thyroid gland is inside or near its (8). Factors such as gender, age, and thyroid volume affect hypothyroidism after radiation therapy, but radiation exposure to the thyroid is a proven risk factor (9). Ionizing radiation to the neck is a known risk factor for hypothyroidism, especially when exposed to it in childhood (2).…”

“…A total of 24 patients (34.8%) experienced hypothyroidism twelve months following radiation therapy. The incidence of hypothyroidism in individuals with NPC following RT was significantly influenced by the thyroid gland's volume and mean dosage (Dmean) (9).…”

A machine learning approach for predicting radiation-induced hypothyroidism in patients with nasopharyngeal carcinoma undergoing tomotherapy

“…Among them, Vx (referring to the percentage of thyroid volume exposed to a dose higher than xGy) is a dosimetric predictive parameter commonly used in many studies 16 – 21 . Additionally, researchers have developed NTCP models to predict RIHT and optimize the radiation dose for the thyroid based on risk factors 22 – 24 . However, relying solely on physical dose parameters from dose-volume histograms (DVH) may only provide partial information about dose distribution and lack information about voxel spatial relationships.…”