Analysis of correlative risk factors for radiation-induced hypothyroidism in head and neck tumors

The aim of the study is to identify clinical and dosimetric factors that could predict the risk of radiation-induced hypothyroidism(RIHT) in head and neck cancer(HNC) patients following intensity-modulated radiotherapy(IMRT).

A total of 103 HNC patients were included in our study. General clinical characteristic and dosimetric data of all recruited patients were analyzed, respectively. The univariate and multivariate logistic regression anlalysis were successively conducted to identify optimal predictors, which aim to construct the nomogram. And the joint prediction was performed.

The incidence of patients with HNC was 36.9% (38/103). Among the clinical factors, gender, N stage, chemotherapy, frequency of chemotherapy and surgery involving the thyroid were related to RIHT. Logistic regression analysis showed that thyroid volume, Dmean, VS₄₅, VS₅₀, VS₆₀ and V_30,60 were independent predictors of RIHT, which were also incorporated in the nomogram. An AUC of 0.937 (95%CI, 0.888–0.958) also was showed outstanding resolving ability of the nomogram. When the volume of the thyroid was greater than 10.6 cm³, the incidence of RIHT was 14.8%, and when the volume of the thyroid was equal to or smaller than 10.6 cm³, the incidence was 72.5%. The incidence rates of RIHT in the group with VS₆₀≦8.4cm³ and VS₆₀ > 8.4cm³ were 61.4% and 19.3%, respectively.

Thyroid volume and thyroid VS₆₀ are independent predictors of RIHT in patients with HNC. Moreover, more attention should be paid to patients with thyroid volume ≤ 10.6cm³. Thyroid VS₆₀ > 8.4cm³ may be a useful threshold for predicting the development of RIHT. The nomogram conducted by the research may become a potential and valuable tool that could individually predict the risk of RIHT for HNC patients.