OBJECTIVE To investigate the relationship between the expression level of endotoxin and soluble interleukin-2 receptor(sIL-2R)and the occurrence of suppurative otitis media in patients with nasopharyngeal carcinoma after radiotherapy.METHODS Seventy-nine nasopharyngeal cancer patients who received radiotherapy in Nanyang Downtown Hospital between January 2022 and July 2023 were selected as the study subjects,and they were followed up for a period of 1 year,and then grouped according to the occurrence of suppurative otitis media during the follow-up period,i.e.,21 cases in the occurringgroup and 58 cases in the non-occurring group,and the baseline data of patients in the two groups were compared,and the levels of endotoxin and sIL-2R were detected at the end of radiotherapy and analyze the relationship between endotoxin,sIL-2R and the occurrence of purulent otitis media after radiotherapy for nasopharyngeal carcinoma.RESULTS A total of 21 cases(26.58%)of 79 nasopharyngeal carcinoma patients developed suppurative otitis media after radiotherapy.Compared with the non-occurrence group,the radiotherapy time,endotoxin,sIL-2R,TNM stage Ⅲ,Eustachian tube involvement,nasal cavity structural abnormality,inflammatory reaction,and palatal sail tensor atrophy degree≥30%were high in the occurrence group,and the difference was statistically significant(all P<0.05).The results of logistic multifactorial analysis showed that inflammatory reaction,endotoxin,abnormal nasal structure,TNM stage(Ⅲ),sIL-2R,Eustachian tube involvement,duration of radiotherapy,and degree of atrophy of palatofacial tensor atrophy≥30%were all risk factors for suppurative otitis media.The results of Spearman's rank correlation analysis showed that endotoxin and sIL-2R were positively correlated with the occurrence of septic otitis media(r=0.493,0.516,P<0.001).Analysis using the ROC curve showed that:endotoxin:AUC value:0.657,sensitivity:61.90%,specificity:72.41%,accuracy:69.62%,95%CI=0.523-0.791;sIL-2R:AUC value:0.697,sensitivity:71.43%,specificity:67.24%,accuracy:68.35%,95%CI=0.566-0.829;combined test:AUC value:0.804,sensitivity:95.24%,specificity:65.52%,accuracy:73.42%,95%CI=0.705-0.903,the best value of the two combined tests.CONCLUSION The elevated levels of endotoxin and sIL-2R in patients with nasopharyngeal carcinoma after radiotherapy may be associated with suppurative otitis media.