Internal Lymphedema Assessment Through Magnetic Resonance Imaging(MRI)and Its Relationship With Long-term Swallowing Function In Patients With Nasopharyngeal Carcinoma After Intensity-modulated Radiation Therapy(MRIT)

Purpose: Head and neck internal lymphedema and the following dysfunctions are the common complications in NPC patients after radiotherapy.However,studies about how to evaluate the edema and its relationship with the quality of life in NPC patients are few.The purpose of this study is to propose a new image based method to evaluate internal edema using MRI and to explore its relationship with patients’ long-term swallowing function and the dose limit of pharyngeal constrictor in patients with NPC.Our study aimed to provide theoretical basis for the prevention and treatment of lymphedema after radiotherapy.Material and Methods: 207 nasopharyngeal carcinoma patients who were initially treated in the Affiliated Cancer Hospital of Nanjing Medical University from 2013 to2015 were selected for retrospective analysis.MRI imaging data and other clinical data of patients before and 1,3,6,9 and 12 months after treatment were collected.The degree of edema was firstly evaluated using the MRI T2 images.Internal lymphedema were measured in the T1 sagittal position,including the thickness of the epiglottic root and the anterior vertebral soft tissue at the third and fourth cervical vertebrae(C3-C4)level.Swallowing and nutrition dysfunction were assessed using the Vanderbilt Head and Neck Symptom Survey,version 2.0 questionnaire.Treatment Planning System(TPS)system was used to delineate the pharyngeal constrictors as an organ at risk.The irradiated dose of pharyngeal constrictors in each patient was collected for further analysis.All data were statistically analyzed using SPSS 22.0software,and the measurement data were shown in the form of (?)± s.The ratio changes before and after radiotherapy for internal head and neck lymphedema were tested by t-test,the internal consistency test for VHNSS2.0 investigation symptom group was conducted,and the correlation analysis was adopted to analyze the correlation between the ratio changes and the severity of swallow dysfunction.P<0.05(bilateral test)was determined as statistically significant.Results: A total of 82 NPC patients were eligible for enrollment,within which,63 were males and 19 were females.The male-to-female ratio was 3.3:1 and the median age of NPC patients is 48.6 years old.All patients were treated with IMRT.The mean thickness of epiglottis root was 4.8±0.87 mm 、 5.4±0.74 mm 、 5.9±0.86 mm 、7.3±1.22mm、6.1±0.96mm、5.5±0.85 mm before and 1,,3,6,9,12 months after radiotherapy,the mean thickness of epiglottis root was 3.8±0.76 mm,4.3±0.83 mm,5.5±1.38 mm,7.2±1.55 mm,5.7±1.62 mm,4.8±1.36mm;the mean thickness of intravertebral soft tissue(C3-7 1.62 mm,4.8 1.36 mm.The results of both groups showed that the edema of internal tissues reached its peak at 6 months after radiotherapy,and then gradually eliminated.All patients completed the evaluation of Vanderbilt Head and Neck Symptom Survey Version 2.0,and the results of consistency test showed that Cronbach alpha values of swallowing solid,swallowing liquid and nutritional symptom groups were 0.9,0.7 and 0.88,respectively,suggesting a good consistency in each symptom groups.Deep edema in head and neck(anterior C3-C4 soft tissue thickness)6 months after radiotherapy was positively correlated with long-term nutrition(β=0.80,p<0.05),swallowing solids(β=0.74,p<0.05),swallowing fluid symptoms(β =0.43,p<0.05)and other swallowing functions.The increased ratio of epiglottic thickness at 6 months after radiotherapy was positively correlated with the nutritional symptoms group(β = 0.31,p< 0.05),and there was no significant correlation with the swallowing solid and liquid symptom groups.We found a positive correlation between the C3-C4 soft tissue thickness ratio and the average irradiated dose of pharyngeal constrictors(β=0.95,p<0.001).Patients with pharyngeal constrictor dose over 60 Gy experienced significantly more dysphagia symptoms..Conclusions : This study proposes MRI base method to evaluate the internal lymphedema in nasopharyngeal carcinoma patients after IMRT.Our preliminary results showed that the severity of deep edema at 6 months after radiotherapy is positively correlated with the long-term nutrition and swallowing dysfunction.Moreover,the higher the dose of pharyngeal constrictor,the more severe in symptoms of lymphedema and swallowing dysfunction.Therefore,attention should be paid to the protection of pharyngeal constrictors during the radiotherapy in nasopharyngeal carcinoma patients.According to the result of this study and the experience of our cancer center,we recommend 60 Gy as the dose limit of pharyngeal constrictor since there is no difference in dysphagia between the two studied dose group.