Dose-volume derived nomogram as a reliable predictor of radiotherapy-induced hypothyroidism in head and neck cancer patients

Abstract

Purpose:

The aim of this study was to determine the possible predictive value of various dosimetric parameters on the development of HT in patients with squamous cell head and neck carcinoma (HNSCC) treated with (chemo)radiotherapy.

Methods:

This study included 156 patients with HNSCC who were treated with (chemo)radiotherapy in a primary or postoperative setting between August 2012 and September 2017. Dose-volume parameters as well as V10 toV70, D02 to D98, and the VS10 to VS70 were evaluated.The patients’ hormone status was regularly assessed during follow-up. A nomogram (score) was constructed, and the Kaplan-Maier curves and Log-Rank tests were used to demonstrate the difference in incidence of HT between cut-off values of specific variables.

Results:

After a median follow-up of 23.0 (12.0 - 38.5) months, 70 (44.9%) patients developed HT. In univariate analysis, VS65, Dmin, V50, and total thyroid volume (TTV) had the highest accuracy in prediciting HT. In a multivariate model, HT was associated with lower TTV (OR 0.31, 95% CI 0.11- 0.87, P=0.026) and Dmin (OR 9.83, 95% CI 1.89-108.08), P=0.042). Hypothroidism risk score (HRS) was constructed as a regression equation and comprised TTV and Dmin. HRS had an AUC of 0.709 (95% CI 0.627 - 0.791). HT occurred in 13 (20.0%) patients with a score<7.1 and in 57 (62.6%) patients with a score >7.1.

Conclusions:

The dose volume parameters VS65, Dmin, V50, and total thyroid volume (TTV) had the highest accuracy in predicting HT. Hypothyroidism risk score may be a useful tool in detecting patients with high risk for radiation-induced hypothyroidism.