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Abstract

Purpose: To establish a multivariate normal tissue complication probability (NTCP) model for radiation-induced hypothyroidism.

Methods and Materials: The thyroid-stimulating hormone (TSH) level of 105 patients treated with (chemo-) radiation therapy for head-and-neck cancer was prospectively measured during a median follow-up of 2.5 years. Hypothyroidism was defined as elevated serum TSH with decreased or normal free thyroxin (T4). A multivariate logistic regression model with bootstrapping was used to determine the most important prognostic variables for radiation-induced hypothyroidism.

Results: Thirty-five patients (33%) developed primary hypothyroidism within 2 years after radiation therapy. An NTCP model based on 2 variables, including the mean thyroid gland dose and the thyroid gland volume, was most predictive for radiation-induced hypothyroidism. NTCP values increased with higher mean thyroid gland dose (odds ratio [OR]: 1.064/Gy) and decreased with higher thyroid gland volume (OR: 0.826/cm(3)). Model performance was good with an area under the curve (AUC) of 0.85.

Conclusions: This is the first prospective study resulting in an NTCP model for radiation-induced hypothyroidism. The probability of hypothyroidism rises with increasing dose to the thyroid gland, whereas it reduces with increasing thyroid gland volume. (C) 2012 Elsevier Inc.

Original languageEnglish
Pages (from-to)E351-E356
Number of pages6
JournalInternational Journal of Radiation Oncology Biology Physics
Volume84
Issue number3
DOIs
Publication statusPublished - 1-Nov-2012

Keywords

  • SUBCLINICAL HYPOTHYROIDISM
  • THYROID-DYSFUNCTION
  • NORMAL TISSUE
  • NECK-CANCER
  • RADIOTHERAPY
  • HEAD
  • LARYNGEAL

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