Dosimetry of Submandibular Glands on Xerostomia for Nasopharyngeal Carcinoma.

Xin-Bin Pan,Shi-Ting Huang,Song Qu,Xiao-Dong Zhu,Yang Liu,Ling Li,Su Pei,Kai-Hua Chen

doi:10.3389/fonc.2020.601403

Abstract

PurposeTo investigate dosimetry of submandibular glands on xerostomia after intensity-modulated radiotherapy for nasopharyngeal carcinoma (NPC).MethodsFrom September 2015 to March 2016, 195 NPC patients were investigated. Xerostomia was evaluated at 12 months after treatment via the RTOG/EORTC system. The least absolute shrinkage and selection operator regression model was used to optimize feature selection for grades 2–3 xerostomia. Multivariable logistic regression analysis was applied to build a predicting model incorporating the feature selected in the least absolute shrinkage and selection operator regression model. Discrimination, calibration, and clinical usefulness of the predicting model were assessed using the C-index, calibration plot, and decision curve analysis.ResultsThe V30 of the parotid glands was selected based on the least absolute shrinkage and selection operator regression. The nomogram displayed good discrimination with a C-index of 0.698 (95% confidence interval [CI]: 0.626–0.771) and good calibration (model 1). Addition of the dosimetric parameters including the mean dose to the submandibular glands, V50 of the submandibular glands, and volume of the submandibular glands to the model 1 failed to show incremental prognostic value (model 2). The model 2 showed a C-index of 0.704 (95% CI: 0.632–0.776). Decision curve analysis demonstrated that the model 1 was clinically useful when intervention was decided at the possibility threshold of > 20%. Within this range, net benefit was comparable between the model 1 and model 2.ConclusionPGv30 was a major predictive factor of grades 2–3 xerostomia for NPC. In contrast, the mean dose to the submandibular glands, V50 of the submandibular glands, and volume of the submandibular glands were not independent predictive factors.

Highlights

Nasopharyngeal carcinoma (NPC) is a radiosensitive cancer, which is high incidence in Southern China [1, 2]
Exclusion criteria were as follows: 1) patients with heart failure, uncontrolled diabetes, severe hepatitis, or renal dysfunction; 2) patients did not complete radiotherapy; 3) patients with a followup time < 1-year; 4) patients with diseases that affected the secretion of salivary glands
The dosimetric parameters included the mean dose to the submandibular glands (SMGmean), V50 of the submandibular glands (SMGv50), volume of the submandibular glands (SMGvolume), mean dose to the parotid glands (PGmean), V30 of the parotid glands (PGv30), V50 of the parotid glands (PGv50), and volume of the parotid glands (PGvolume)

Summary

Introduction

Nasopharyngeal carcinoma (NPC) is a radiosensitive cancer, which is high incidence in Southern China [1, 2]. Radiationinduced xerostomia is a common complication after intensitymodulated radiotherapy (IMRT) [3]. Up to 30% patients suffer from clinically significant xerostomia, which degrades patients’ quality of life [4, 5]. Parotid glands produce 60%–65% of salivary output, while submandibular glands contribute 20%–30% of the salivary output [6, 7]. Previous studies reported that mean dose to the parotid glands was a major predictor of xerostomia [8,9,10,11,12,13]. Dosimetry of submandibular glands on xerostomia for NPC was not well investigated.

Methods

Results

Conclusion