Development of a normal tissue complication probability (NTCP) model for radiation-induced hypothyroidism in nasopharyngeal carcinoma patients

Mei Li,Vincent W C Wu,Zhining Yang,Zhenxi Xu,Xiaoying Gao,Ren Luo,Dandan Wang,Binghui He,Zhixiong Lin

doi:10.1186/s12885-018-4348-z

Abstract

BackgroundThe objectives of this study were to build a normal tissue complication probability (NTCP) model of radiation-induced hypothyroidism (RHT) for nasopharyngeal carcinoma (NPC) patients and to compare it with other four published NTCP models to evaluate its efficacy.MethodsMedical notes of 174 NPC patients after radiotherapy were reviewed. Biochemical hypothyroidism was defined as an elevated level of serum thyroid-stimulating hormone (TSH) value with a normal or decreased level of serum free thyroxine (fT4) after radiotherapy. Logistic regression with leave-one-out cross-validation was performed to establish the NTCP model. Model performance was evaluated and compared by the area under the receiver operating characteristic curve (AUC) in our NPC cohort.ResultsWith a median follow-up of 24 months, 39 (22.4%) patients developed biochemical hypothyroidism. Gender, chemotherapy, the percentage thyroid volume receiving more than 50 Gy (V50), and the maximum dose of the pituitary (Pmax) were identified as the most predictive factors for RHT. A NTCP model based on these four parameters were developed. The model comparison was made in our NPC cohort and our NTCP model performed better in RHT prediction than the other four models.ConclusionsThis study developed a four-variable NTCP model for biochemical hypothyroidism in NPC patients post-radiotherapy. Our NTCP model for RHT presents a high prediction capability.Trial registrationThis is a retrospective study without registration.

Highlights

The objectives of this study were to build a normal tissue complication probability (NTCP) model of radiation-induced hypothyroidism (RHT) for nasopharyngeal carcinoma (NPC) patients and to compare it with other four published NTCP models to evaluate its efficacy
Since the life span expectation of NPC patients has remarkably improved in the last decade due to the emerging of effective chemotherapy and advanced radiotherapy techniques [7], the demand for reducing the radiationinduced side effects including RHT has been increasing
Two NTCP models [16] for RHT based on Hodgkin’s lymphoma patients have been reported. Another two NTCP models based on the thyroid mean dose and thyroid volume have been built for head and neck cancer patients excluding NPC [14, 17]

Summary

Introduction

The objectives of this study were to build a normal tissue complication probability (NTCP) model of radiation-induced hypothyroidism (RHT) for nasopharyngeal carcinoma (NPC) patients and to compare it with other four published NTCP models to evaluate its efficacy. Radiation-induced hypothyroidism (RHT) is one of the common late complications in patients receiving radiotherapy to the neck region, which could be subclinical or clinical. Establishing a normal tissue complication probability (NTCP) model based on both clinical and dose-volume factors may offer an effective method of predicting RHT [21]. Two NTCP models [16] for RHT based on Hodgkin’s lymphoma patients have been reported Another two NTCP models based on the thyroid mean dose and thyroid volume have been built for head and neck cancer patients excluding NPC [14, 17]

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