| Background:In the past 20 years,the introduction of Intensity modulated radiotherapy(IMRT)has significantly improved the survival of patients with nasopharyngeal cancer,but Hypothyroidism(HT)is common after radical radiotherapy for nasopharyngeal cancer,with an incidence of 20-50%.Radical or prophylactic radiotherapy of a positive cervical lymph node can affect the thyroid and cause HT.Since quality of life is an important issue in treatment management,it is important to predict and prevent the occurrence of HT after radiotherapy in patients with NPC.In this study,the changes of thyroid function during radiotherapy were analyzed to investigate the acute response mechanism of thyroid to radiotherapy and to predict the occurrence of hypothyroidism(HT)combined with clinical factors and thyroid dosimetric parameters.Objectives:To explore the dynamic changes of thyroid hormone levels during and after IMRT for nasopharyngeal carcinoma,and to explore the thyroid response in the acute and subacute phase of radiotherapy,so as to find an appropriate opportunity for intervention to prevent hypothyroidism after radiotherapy,so as to better guide the individualized treatment to improve the quality of life of patients.Methods:A total of 111 newly treated patients with nasopharyngeal carcinoma confirmed by nasopharyngeal biopsy pathology in Jiangxi Cancer Hospital from May 1,2019 to December 31,2019 were included.Changes in FT3,FT4,TSH,and Tg Ab levels were assessed before,during,and after radiotherapy.After radiotherapy,111 patients were followed up,and changes in FT3,FT4,TSH and Tg Ab levels were collected to determine the occurrence of HT in the patients.Patients with primary and subclinical hypothyroidism were diagnosed with HT regardless of symptoms,regardless of whether FT4 levels were lower than our lower institutional reference range(0.89--1.76ng/d L)and whether TSH levels were higher than our lower institutional reference range(0.55--4.78 u IU/ m L).Results:1.To observe the changes of thyroid function in 111 patients with nasopharyngeal carcinoma during radical radiotherapy: During the course of radical radiotherapy for nasopharyngeal carcinoma,only 1 patient developed HT at the end of radiotherapy.Before the onset of HT,the thyroid hormones FT3,FT4,TSH,and TGAb all showed a continuous decline.FT3 gradually decreased during radiotherapy,and the mean value was lower than normal from the middle stage to the end of radiotherapy,with statistical significance(P<0.05).FT4 slightly increased in the middle of radiotherapy and decreased at the end of radiotherapy,but there was no statistical significance(P=0.136).TSH decreased significantly from before radiotherapy to the middle of radiotherapy,and slightly increased from the middle of radiotherapy to the end of radiotherapy,with no statistical significance(P=0.371).Tg Ab showed a downward trend in the course of radiotherapy,and the lowest value appeared at the end of radiotherapy,with statistical significance(P <0.05).2.There was no significant difference in hormone levels of FT3,FT4,TSH and Tg Ab before,during and after radiotherapy by gender stratification analysis(all P= >0.05).Stratified analysis based on age showed significant difference in FT3 before and after radiotherapy(P<0.05).FT4 was significantly different before radiotherapy(P=0.001),but no significant difference was found between and after radiotherapy.3.Changes of thyroid function in 111 patients after 1 year of follow-up radiotherapy: FT3 gradually returned to normal after radiotherapy,and the mean value was at normal level during the 1-year follow-up.FT4 showed a gradual decline after the end of radiotherapy,and the average value was lower than normal 6-12 months after the end of radiotherapy.TSH increased after the end of radiotherapy,and the average of 3-12 months was higher than the normal level.Tg Ab remained at normal level after radiotherapy.The 26 patients who eventually developed HT after follow-up were further stratified and analyzed in combination with the changes in thyroid hormone levels before,during and after the radical radiotherapy,which showed that the TSH changes in these patients did not appear to be mild in the early stage during the radical radiotherapy.The performance of the increase in the late stage of the decline,but all manifested as the continuous decline of TSH.4.Logistic regression analysis showed that TNM stage,thyroid volume,were independent predictors of hypothyroidism.Among them,the earlier TNM stage and the larger thyroid volume are the protective factors of thyroid function.Conclusion:Whether the continuous decline of TSH during radiotherapy can be determined as a high-risk factor for HT still needs further research In the later period.With the extension of follow-up time,the incidence of hypothyroidism increased continuously.The incidence of HT after radiotherapy for nasopharyngeal carcinoma was significantly correlated with TNM stage,thyroid volume.For nasopharyngeal carcinoma patients with thyroid volume <14.49 cm3,respectively,more dose and volume restriction should be given. |
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