Factors predictive of the development of hypothyroidism after intensity-modulated radiation therapy for pharyngeal cancer

Abstract

Background

Hypothyroidism is a common adverse event after radiotherapy for head and neck tumors and the incidence need to be re-evaluated because of using intensity-modulated radiotherapy (IMRT).

Aims/Objectives

Confirm the dose-volume effect of IMRT for pharyngeal cancer on hypothyroidism.

Materials and methods

This was a retrospective analysis of patients underwent IMRT for pharyngeal cancer from June 2011 to May 2018. Patients were classified into group A (thyroid stimulating hormone (TSH) <5μU/ml), group B (5< =TSH < 10), and group C (10< =TSH) based on TSH over 36 months post-radiation. Radiation dose, thyroid volume, and the proportion of the thyroid that received X Gy or greater (Vx) were measured.

Results

Fifty-two patients were included in this work. Hypothyroidism developed in 33/52 (63%) patients, 13 in group B and 20 in group C. The mean radiation dose to the thyroid was 49.4 Gy and the median time until hypothyroidism was 39 months after irradiation. Hypothyroidism was significantly related to neck dissection (ND) and radiation dose to the thyroid. Patients whose thyroid received 45 Gy or more (V45) >67% had a significantly higher incidence of hypothyroidism.

Conclusions and significance

Patients with pharyngeal cancer who had ND and V45 to the thyroid >67% are at risk of hypothyroidism.

Chinese abstract

背景：甲状腺功能减退是头颈部肿瘤放疗后常见的不良事件。由于使用了强度调制放疗 (IMRT), 因此需要重新评估肿瘤和发病率。

目的：确定 IMRT 治疗咽癌对甲状腺功能减退症的剂量-体积效应。

材料和方法：这是一项对在2011 年 6 月至 2018 年 5 月期间接受 IMRT 治疗咽喉疾病的患者的回顾性分析。根据放疗后 36 个月的 TSH, 将患者分为 A 组（促甲状腺激素 (TSH) <5μU/ml）, B组（5<= TSH < 10）和 C 组（10 < =TSH）。测量了辐射剂量、甲状腺体积和接受 X Gy 或更大 (Vx)的甲状腺所占比例。

结果：本研究共纳入 52 名患者。甲状腺功能减退症发生在于其中33名 (63%)患者, B 组 13 例, C 组 20 例。甲状腺平均辐射剂量为 49.4 Gy 和照射后甲状腺功能减退的中位时间为 39 个月。甲状腺功能减退症与颈部解剖（ND）和甲状腺的辐射剂量显著相关。甲状腺接受 45 Gy 或更多 (V45) >67%的患者的甲状腺功能减退症发生率显著升高。

结论和意义：接受 ND 和甲状腺接受V45>67% 的咽癌患者有甲状腺功能减退症的风险。

Keywords:

• Head and neck cancer
• intensity-modulated radiation therapy
• hypothyroidism
• radiation dose

Acknowledgement

Authors would like to thank Grant-in-Aid for Scientific Research for funding.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by Grant-in-Aid for Scientific Research (C), JSPS KAKENHI [20K08009].