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.
Highlights
Radiotherapy-induced hypothyroidism (RHT) is one of the common late-stage toxic reactions in patients who have received cervical radiotherapy, and its incidence is as high as 20%–40% [1,2,3], which is higher than the incidence in the normal population
This study aims to assess the incidence of hypothyroidism after radiotherapy in patients with nasopharyngeal carcinoma, analyze the correlation between hypothyroidism after radiotherapy and possible influencing factors, and construct a normal tissue complication probability (NTCP) model for the occurrence of hypothyroidism after Intensity-modulated radiation therapy (IMRT), based on the equivalent dose in 2 Gy fractions (EQD2)
The clinical diagnosis of hypothyroidism depends on the related symptoms and signs of hypothyroidism, the extent to which the serum thyroid stimulating hormone (TSH) is higher than the normal upper limit, and the extent to which free triiodothyronine 3 (fT3) and free triiodothyronine 4 (fT4) are lower than the normal lower limit
Summary
Radiotherapy-induced hypothyroidism (RHT) is one of the common late-stage toxic reactions in patients who have received cervical radiotherapy, and its incidence is as high as 20%–40% [1,2,3], which is higher than the incidence in the normal population. 70% to 80% of patients with nasopharyngeal carcinoma had cervical lymph node metastasis at the first diagnosis [7, 8], and prophylactic irradiation of the neck lymph node drainage area is inevitable. The thyroid is located in the prophylactic irradiation area of the neck and is exposed to higher doses of radiation. There are currently few reports on the incidence of hypothyroidism in nasopharyngeal cancer patients after IMRT. Huang et al retrospectively analyzed the data of 98 nasopharyngeal cancer patients who received IMRT. The lower neck prophylactic irradiation area was given a prescribed dose of 54 Gy. The median follow-up period was 17 months, and the results showed that the average thyroid dose was 49.72 Gy, and the incidence of hypothyroidism was 33.7% [9]. Hypothyroidism due to radiotherapy generally has an insidious onset and lacks typical symptoms and signs; it is often ignored by clinicians and patients
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
