Apparent diffusion coefficient histogram analysis can evaluate radiation-induced parotid damage and predict late xerostomia degree in nasopharyngeal carcinoma.

Nan Zhou,Huanhuan Zheng,Xin Dou,Jing Yan,Baorui Liu,Song Liu,Xiaofeng Yang,Ming Li,Chen Chu,Tingting Guo,Lijing Zhu,Weibo Chen,Jian He,Xia Pan,Zhengyang Zhou

doi:10.18632/oncotarget.19602

Abstract

We investigated apparent diffusion coefficient (ADC) histogram analysis to evaluate radiation-induced parotid damage and predict xerostomia degrees in nasopharyngeal carcinoma (NPC) patients receiving radiotherapy. The imaging of bilateral parotid glands in NPC patients was conducted 2 weeks before radiotherapy (time point 1), one month after radiotherapy (time point 2), and four months after radiotherapy (time point 3). From time point 1 to 2, parotid volume, skewness, and kurtosis decreased (P < 0.001, = 0.001, and < 0.001, respectively), but all other ADC histogram parameters increased (all P < 0.001, except P = 0.006 for standard deviation [SD]). From time point 2 to 3, parotid volume continued to decrease (P = 0.022), and SD, 75th and 90th percentiles continued to increase (P = 0.024, 0.010, and 0.006, respectively). Early change rates of parotid ADCmean, ADCmin, kurtosis, and 25th, 50th, 75th, 90th percentiles (from time point 1 to 2) correlated with late parotid atrophy rate (from time point 1 to 3) (all P < 0.05). Multiple linear regression analysis revealed correlations among parotid volume, time point, and ADC histogram parameters. Early mean change rates for bilateral parotid SD and ADCmax could predict late xerostomia degrees at seven months after radiotherapy (three months after time point 3) with AUC of 0.781 and 0.818 (P = 0.014, 0.005, respectively). ADC histogram parameters were reproducible (intraclass correlation coefficient, 0.830 - 0.999). ADC histogram analysis could be used to evaluate radiation-induced parotid damage noninvasively, and predict late xerostomia degrees of NPC patients treated with radiotherapy.

Highlights

Xerostomia is a common complication of radiotherapy in patients with nasopharyngeal carcinoma (NPC), which can cause difficult swallowing, tooth decay, and even sleep disorders [1]
Parotid skewness and kurtosis decreased (P = 0.001, and < 0.001, respectively), and all the other apparent diffusion coefficient (ADC) histogram parameters increased from time point 1 to 2, and standard deviation (SD), 75th, and 90th percentiles continued to increase from time point 2 to 3 (P = 0.024, 0.010, and 0.006, respectively)
ADC histogram analysis has been successfully introduced into the evaluation of radiation-induced parotid damage in NPC patients undergoing radiotherapy

Summary

Introduction

Xerostomia is a common complication of radiotherapy in patients with nasopharyngeal carcinoma (NPC), which can cause difficult swallowing, tooth decay, and even sleep disorders [1]. An objective evaluation of radiationinduced parotid damage and early prediction of late xerostomia degrees could provide a significant advantage in performing timely intervention to avoid long-term xerostomia. Histopathological examination can evaluate the microstructure changes of irradiated parotid glands, which involves an invasive procedure [7]. Scintigraphy can quantitatively assess the functional changes of irradiated parotid glands, but this technique involves extra radiation exposure [8]. Magnetic resonance (MR) imaging, can be an objective, noninvasive, and effective tool in evaluating radiation-induced parotid damage [9]. MR sialography, dynamic contrast-enhanced, diffusion-weighted (DW), intravoxel incoherent motion (IVIM), and T1rho MR imaging have been successfully attempted to evaluate the changes of radiation-induced parotid damage [10,11,12,13,14,15]. State of the art recent diffusion imaging uses IVIM, so that the real diffusion of diffusivity (D) can be distinguished from the vascular contamination (D*), providing additional information on the bloodflow and blood volume (perfusion)

Methods

Results

Conclusion