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Background and Purpose nasopharyngeal carcinoma (nasopharygealcancer, NPC) is one of the most common malignancy in southern China, and radiation therapy is the main treatment, but more than 75% of patients in treatment when combined with cervical lymph node metastasis, in which cases, radiation therapy is inevitably part of or the entire thyroid is included in the radiation field, and sometimes thyroid by radiation dose up to 60Gy or even higher. Many scholars have observed that part of the occurrence of hypothyroidism in the long-term survival of patients with diseases such as thyroiditis or thyroid nodules. A low is the most common complication, typical signs and symptoms of cold, less words, fatigue, lack of facial expression cold, dry skin, memory loss, mental retardation, sinus bradycardia, anorexia, bloating, constipation, and sexual desire loss and so reduce the patient's quality of life. In recent years, with the improvement of radiation therapy technology, extend the survival of patients, increasing attention has been paid to how to improve the quality of life of patients, but for changes in thyroid function after radiotherapy with radiotherapy dose relationship was relatively small. In this study, mainly through the monitoring of patients with nasopharyngeal carcinoma before radiotherapy, after radiotherapy, 3, 6, 12 and 18 months in serum FT3, FT4, TSH concentration change about changes in thyroid function, at the same time by the end of radiotherapy radiotherapy understand the morphological changes of the thyroid, 6, 12, and 18-month change of thyroid volume and thyroid doses to explore the relationship between the of thyroid irradiation dose and changes in thyroid function analysis of the treatment planning system (TPS). Objects and methods to collect our hospital from February 2008 to August 2008, to accept radical chemoradiotherapy for nasopharyngeal carcinoma in 30 patients, all patients were confirmed by pathological examination, who had no history of head and neck surgery, endocrine history of thyroid disease history. ECLIA detection before radiotherapy, the serum of 3, 6, 12 and 18 months after the end of radiotherapy, FT3, FT4, TSH concentration, at the same time through a CT scan records before radiotherapy, 6, 12, and 18 months after radiotherapy thyroid volume and thyroid irradiation dose by the treatment planning system (TPS) analysis to study the relationship between thyroid radiation dose and thyroid function changes. Results. Thyroid volume after radiotherapy overall downward trend, the thyroid before radiotherapy average volume of 17.2533 ± 9.06402cm3, to 6 months after radiotherapy reduced 14.1842 ± 6.34759cm3, but not statistically significant (p = 0.083); to 12 months after radiotherapy, and 18 months, respectively, to 12.8732 ± 5.64541cm3 12.5698 ± 5.53825 cm3, began to have a statistically significant (p values ??were 0.014,0.009). 6 months after radiotherapy, 12 months, 18-month changes in thyroid volume and thyroid average radiation dose (P values ??were 0.034,0.002,0.001 corresponding correlation coefficient r = -0.389, -0.544, -0.594) the maximum radiation dose is not related to (the p values ??0.087,0.674,0.135, the corresponding correlation coefficient r = -0.318, -0.080, -0.280). 2.FT3 level 3 months after radiotherapy, 6 months mild change, but not statistically significant (p values ??were 0.857,0.790) to 12 months after radiotherapy decreased significantly (p = 0.004) , but in the 18 months after radiotherapy FT3 appeared significantly higher (p = 0.020), and recovered to the level before treatment, compared with before treatment was not statistically significant (p = 0.570). The one-way ANOVA LSD method detected 12 months FT3 levels after radiotherapy and several other time periods were statistically significant (p lt; 0.05) FT3 levels and thyroid radiation dose. 3.FT4 level varies from 3 months after radiotherapy began to decline, but not statistically significant (p = 0.079), increased slightly from 3 months to 6 months after radiotherapy (p = 0.287), now to 12 months after radiotherapy significantly decreased (p = 0.002). 12 months to 18 months after radiotherapy again mild recovery, the recovery rate compared to the last change before the relatively small radiation still statistically significant difference (p = 0.012). 12 months after radiotherapy FT4 changes associated with thyroid average radiation dose (p = 0.010, r = -0.461). 4. TSH level after radiotherapy overall upward trend from 3 months after radiotherapy mild upward trend, but not statistically significant (p = 0.983), to 12 months after radiotherapy was statistically significant (p = 0.002), 18 months after radiotherapy, the highest (p = 0.000). The correlation analysis found that TSH changes 12 months after radiotherapy with thyroid average radiation dose was linearly correlated (p = 0.038, r = 0.381). The conclusions of this study showed that patients with nasopharyngeal carcinoma accept radical radiotherapy can cause a decline in the function of the thyroid, specific performance thyroid volume and thyroid hormone levels change; dose-dependent radiation-induced hypothyroidism can also be seen from the results of this study phenomenon on the clinical design of radiation treatment planning should be to minimize the the Thyroid average radiation dose to effectively reduce the incidence of radiation-induced hypothyroidism; In addition to this study proposed the thyroid dose limits in radiotherapy, namely 33Gy , which provides for the protection of our better after radiotherapy plans to develop, thyroid reference.
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