Analysis Of Influencing Factors Of Radiation Caries After Intensity Modulated Radiotherapy For Nasopharyngeal Carcinoma

Background: Nasopharyngeal carcinoma(NPC)is one of the most common head and neck tumors in southern China,especially in Guangdong area.At present,radiotherapy is the first choice of treatment for nasopharyngeal carcinoma.With the development of technology,intensity modulated radiation therapy has become the mainstream of radiotherapy for nasopharyngeal carcinoma patients because of its ability to protect normal tissues.With the improvement of survival rate,severe adverse reactions such as dry mouth,skin mucosal reaction,radiation otitis media,radiation encephalopathy and so on have been paid more and more attention.Radiation caries are also one of the common adverse reactions after radiotherapy,which may seriously affect the quality of life of patients,but receive less attention.Objective:To understand the influencing factors of radiation caries in patients with nasopharyngeal carcinoma after intensity-modulated radiotherapy.To analyze the correlation between these factors and the occurrence of radiation caries,especially the effects of dosimetry,and to put forward the possible dose limiting conditions and preventive measures.Methods:From January 2015 to December 2017,169 patients with NPC received intensity-modulated nasopharyngeal radiotherapy in the Cancer Center of Guangzhou Medical University were included in this study.All the patients underwent oral examination before radiotherapy in the stomatology department and recorded the dental conditions before radiotherapy.The radiation caries were followed up according to the rules after radiotherapy and the incidence of radiation caries was recorded at each time point.In addition to the delineation of the target area and the organ at risks(OARs),the upper and lower dentition are distinguished and delineated separately as the OAR.Dose data of parotid gland and upper and lower dentition were collected and recorded in treatment planning system(TPS).SPSS 19.0 software package was applied for analysis sex,age,chemotherapy,smoking,the dose of parotid gland and upper and lower teeth(such as Dmin Dmax Dmean)by Logistic regression one by one.The factors with statistical significance were screened out by Logistic regression multivariate analysis,and the possible factors affecting the occurrence of radiation caries were screened out.The relationship between the occurrence of radiation caries and these possible factors,especially the influence of dosimetric factors,were analyzed.The possible dose-limiting conditions and preventive measures were put forward.Results: 169 NPC patients were included in this study,including 124 males and 45 females.The median age was 48 years old(17~79 years old).The median follow-up time was 18.23 months(3.28 ~ 38.67 months).The caries rate of the whole group was 28.99%(49/169),and the dental caries rate was 4.38%(196/4475),13.17%(196/1488)of DT in DMFT,62.70%(933/1488)of MT in DMFT and 24.13%(359/1488)of FT in DMFT respectively.The mean DMFT of 169 patients was 8.54 ±6.80.According to the occurrence of radiation caries,the patients were divided into caries group and non-caries group.Univariate analysis and multivariate analysis showed that age(p=0.042),smoking(p=0.049),and the average dose of upper dentition(p=0.043)were independent prognostic factors of radiation caries after radiotherapy.Conclusions:In this study,the incidence of radiation caries was 28.99%.The incidence of radiation caries was probably correlated with age,smoking and the average dose of upper dentition.Sex,clinical stage,chemotherapy,Dmin,Dmax,Dmean of parotid gland,Dmin,Dmax,Dmean of upper and lower dentition were not the risk factors of radiation caries.In order to reduce the incidence of radiation caries and improve the quality of life of patients with NPC after radiotherapy,it is suggested to reduce dental dose and quit smoking as far as possible.