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Int J Radiat Oncol Biol Phys. 2012 Nov 1;84(3):e351-6. doi: 10.1016/j.ijrobp.2012.05.020. Epub 2012 Jun 19.

A prospective cohort study on radiation-induced hypothyroidism: development of an NTCP model.

Author information

1
Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.

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.

PMID:
22717243
DOI:
10.1016/j.ijrobp.2012.05.020
[Indexed for MEDLINE]

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