V30 as a predictor for radiation-induced hypothyroidism: a dosimetric analysis in patients who received radiotherapy to the neck

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.

Thyroid V50 Highly Predictive of Hypothyroidism in Head-and-Neck Cancer Patients Treated With Intensity-modulated Radiotherapy (IMRT)

“…Several series have reported a >40% incidence rate of treatment-induced hypothyroidism. [5][6][7][8][9] Although ultrasensitive laboratory testing and precise pharmacologic dosing have been important in early diagnosis and treatment, the condition can still present with serious clinical manifestations such as arrhythmias and acute psychiatric issues. 15,17,20 Moreover, diagnosis can necessitate lifelong laboratory testing and pharmacologic treatment.…”

“…In certain series, up to 40% to 50% of patients developed hypothyroidism after concurrent chemotherapy and radiation for head-and-neck malignancies. [5][6][7][8][9][10][11] Currently used thyroid dose constraints are largely derived from historic studies and cohorts treated for other indications such as with mantle and neck radiation for the Hodgkin disease. 9,12 There are far less applicable data from modern series examining the outcomes after treatment with IMRT and even more sparse data in the setting of treatment with concurrent chemotherapy.…”

A dosimetric study on radiation‑induced hypothyroidism following intensity‑modulated radiotherapy in patients with nasopharyngeal carcinoma

“…For instance, the prescribed dose for Hodgkin lymphoma ranged from 30-36 Gy, whereas the recommended dose for head and neck tumor types was 54-70 Gy; therefore, the volume parameters reported by Cella et al (24) was notably reduced. The Dmean has also been reported as an independent predictor for RIHT (27,28); however, the associated threshold value has rarely been studied. Fujiwara et al (29) estimated the threshold value as 30 Gy, based on the incidence of RIHT being significantly reduced in patients with Dmean <30 Gy compared with the other groups (P<0.05).…”

Nomogram for radiation-induced hypothyroidism prediction in nasopharyngeal carcinoma after treatment

“…10,15 Threedimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) enable the analysis of dose-volume factors. The minimum dose (D min ) and mean dose (D mean ), the percentage of thyroid volume receiving .30, 45 or 50 Gy, the absolute thyroid volume spared from 45 Gy or less and volume spared from 60 Gy or less 13,14,[16][17][18][19][20][21][22][23][24] were found to be dosimetric predictors for RHT. However, predictors and dose constraints varied according to the study.…”

“…However, predictors and dose constraints varied according to the study. 13,14,[16][17][18][19][20][21][22][23][24][25] Nasopharyngeal carcinoma (NPC) is a prevalent cancer in southern China. Irradiation to the bilateral neck is a regular practice because of a high incidence 26 of neck node involvement.…”