Abstract
IntroductionThe purpose of this study is to evaluate the possible predictors of thyroid disorders after neck radiotherapy, with a focus on radiation dose-volume factors.MethodsThyroid function was measured in 100 patients who had received radiotherapy to the neck, including the thyroid. All radiation-induced thyroid dysfunctions were determined with an endpoint of abnormal thyroid stimulating hormone (TSH), free triiodothyronine (fT3) and thyroxine (fT4) and thyroid peroxidase antibodies and (TPA). The total volume of the thyroid, mean radiation dose to the thyroid (Dmean) and thyroid volume percentage that received radiation doses of 10–50 Gy (V10-V50) were calculated in all patients. The evaluated risk factors for thyroid dysfunction included dose-volume parameters, sex, age, previous surgery, chemotherapy and comorbidity.ResultsThere were 52 patients with hypothyroidism and V30 (p = 0.03), thyroid volume (p = 0.01) and Dmean (p = 0.03) appeared to be correlated with hypothyroidism in univariate analysis. However, there was not association found in multivariate analysis for these factors.ConclusionsThyroid disorders after radiation therapy to the neck still represent a clinically underestimated problem. V30 may be a useful tool for evaluating the risk of hypothyroidism when determining an individual patient’s treatment.
Highlights
The purpose of this study is to evaluate the possible predictors of thyroid disorders after neck radiotherapy, with a focus on radiation dose-volume factors
Some dosimetric studies exploring radiation-induced thyroid dysfunction have suggested that a thyroid dose of ≥30 Gy is associated with higher risk for hypothyroidism [1,4,6,7]
Kim et al [8] found that the percentage of thyroid volume absorbing >45 Gy was observed to be the optimal variable for predicting the development of hypothyroidism, and they suggested a V45 of 50% as a possible dose-volumetric threshold for radiation-induced hypothyroidism
Summary
The purpose of this study is to evaluate the possible predictors of thyroid disorders after neck radiotherapy, with a focus on radiation dose-volume factors. The thyroid gland is one the most radiosensitive normal tissues in the human body It is frequently affected by radiotherapy in head and neck patients, and thyroid dysfunctions are commonly seen following irradiation [1,2]. The incidence of radiation-induced hypothyroidism has been described mostly within the range of 20–30% and the reports are currently increasing in literature [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25]. Some dosimetric studies exploring radiation-induced thyroid dysfunction have suggested that a thyroid dose of ≥30 Gy is associated with higher risk for hypothyroidism [1,4,6,7].
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