Incidence of and Risk Factors for Mastoiditis after Intensity Modulated Radiotherapy in Nasopharyngeal Carcinoma.

Ji-Jin Yao,Lei Chen,Lu-Lu Zhang,Yan-Ping Mao,Xiao-Li Yu,Jun Ma,Ying Sun,Jian-Yong Shao,Li Lin,Guan-Qun Zhou,Ying Guo,Ling-Long Tang

doi:10.1371/journal.pone.0131284

Abstract

PurposeTo report the incidence of and risk factors for mastoiditis after intensity-modulated radiotherapy (IMRT) in nasopharyngeal carcinoma (NPC).Patients and MethodsRetrospective analysis of pretreatment and follow-up magnetic resonance imaging (MRI) data for 451 patients with NPC treated with IMRT at a single institution. The diagnosis of mastoiditis was based on MRI; otomastoid opacification was rated as Grade 0 (none), 1 (mild), 2 (moderate) or 3 (severe) by radiologists blinded to clinical outcome. This study mainly focused on severe mastoiditis; patients were divided into three groups: the G0M (Grade 0 mastoiditis before treatment) group, G1-2M (Grade 1 to 2 mastoiditis before treatment) group and G3M (Grade 3 mastoiditis before treatment) group. The software SAS9.3 program was used to analyze the data.ResultsFor the entire cohort, the incidence of Grade 3 mastoiditis was 20% before treatment and 31%, 19% and 17% at 3, 12 and 24 months after radiotherapy, respectively. In the G0M group, the incidence of severe mastoiditis was 0% before treatment and 23%, 15% and 13% at 3, 12 and 24 months after radiotherapy, respectively. Multivariate analysis revealed T category (OR=0.68, 95% CI = 0.469 to 0.984), time (OR=0.668, 95% CI = 0.59 to 0.757) and chemotherapy (OR=0.598, 95% CI = 0.343 to 0.934) were independent factors associated with severe mastoiditis in the G0M group after treatment.ConclusionsMastoiditis, as diagnosed by MRI, occurs as a progressive process that regresses and resolves over time in patients with NPC treated using IMRT.

Highlights

Nasopharyngeal carcinoma (NPC) has an extremely unbalanced endemic distribution and is most prevalent in southern China where the incidence is between 15 and 50 per 100,000 [1]
Multivariate analysis revealed T category (OR=0.68, 95% CI = 0.469 to 0.984), time (OR=0.668, 95% CI = 0.59 to 0.757) and chemotherapy (OR=0.598, 95% CI = 0.343 to 0.934) were independent factors associated with severe mastoiditis in the G0M group after treatment
We conducted a retrospective study to investigate the incidence of severe mastoiditis at different intervals after intensity-modulated radiotherapy (IMRT) and to identify risk factors associated with mastoiditis after IMRT

Summary

Introduction

Nasopharyngeal carcinoma (NPC) has an extremely unbalanced endemic distribution and is most prevalent in southern China where the incidence is between 15 and 50 per 100,000 [1]. The introduction of intensity-modulated radiotherapy (IMRT) has greatly improved the ability to distribute radiation doses more precisely [7, 8]. Compared to two-dimensional conventional radiotherapy (2D-CRT), IMRT can reduce the volume of the area of the mastoid receiving a high dose and decrease the risk of toxicity [8]. Previous research on mastoiditis has mostly been based on patients treated with 2D-CRT, and data on the incidence and tumor-related factors associated with mastoiditis after IMRT are lacking. We conducted a retrospective study to investigate the incidence of severe mastoiditis at different intervals after IMRT and to identify risk factors associated with mastoiditis after IMRT.

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