Abstract:

Objective To investigate the dynamic changes of oral saliva flow， pH value， and bacterial flora before and after radiotherapy in patients with nasopharyngeal carcinoma （NPC） treated with intensity modulated radiotherapy， and to analyze the influencing factors of severe radioactive oral mucositis. Methods One hundred NPC patients who received radiotherapy for the first time in the Head and Neck Radiotherapy Ward of Shandong Cancer Hospital and Institute from June 2， 2021 to December 30， 2022 were selected. Oral saliva flow， pH value and bacterial flora were measured at 5 time points， namely before radiotherapy， 15 times of radiotherapy， 35 times of radiotherapy， 1 month and 3 months after radiotherapy in patients with NPC， and the dynamic changes of 3 indicators were analyzed at each time. The factors of the occurrence of severe radioactive oral mucositis in patients with NPC were analyzed by univariate and multivariate logistic regression 15 times of radiotherapy. Results The saliva flow of patients with NPC before radiotherapy， 15 times of radiotherapy， 35 times of radiotherapy， 1 month after and 3 months after radiotherapy were （16.51±1.29）， （8.64±1.31）， （5.15±1.14）， （4.78±1.36） and （5.67±1.27） ml， respectively， with a statistically significant difference （F=2 171.94， P<0.001）. Oral saliva flow decreased to the lowest level 1 month after radiotherapy and then increased （all P<0.05）. The pH values of patients with NPC before radiotherapy， 15 times of radiotherapy， 35 times of radiotherapy， 1 month after and 3 months after radiotherapy were 8.28±0.67， 5.87±0.53， 5.32±0.55， 6.04±0.83， 6.74±0.63， respectively， with a statistically significant difference （F=370.43， P<0.001）. The pH value decreased successively after 15 and 35 times of radiotherapy， and gradually increased 1 month and 3 months after radiotherapy （all P<0.05）. There was a statistically significant difference （χ²=18.24， P<0.001） in the detection rate of pathogenic bacteria in patients with NPC before radiotherapy （6%， 6/100）， 15 times of radiotherapy （62%， 62/100）， 35 times of radiotherapy （60%， 60/100）， 1 month after radiotherapy （40%， 40/100） and 3 months after radiotherapy （29%， 29/100）. Compared with before radiotherapy， there were statistically significant differences in the detection rates of pathogenic bacteria between 15 times of radiotherapy and 35 times of radiotherapy （χ²=1.90， P=0.001； χ²=1.63， P=0.005）. There was no statistically significant difference in the detection rate of pathogenic bacteria between 15 times of radiotherapy and 35 times of radiotherapy （χ²=0.27， P=0.644）. Compared with before radiotherapy， there was no statistically significant difference in the detection rate of pathogenic bacteria 1 month after radiotherapy and 3 months after radiotherapy （χ²=1.30， P=0.024； χ²=0.83， P=0.149）. Of 100 cases of NPC radiotherapy， 70 patients developed severe radiation oral mucositis （≥ grade 3）. There were statistically significant differences in severe radioactive oral mucositis among patients with different smoking history （χ²=8.84， P=0.003）， alcohol drinking （χ²=23.94， P<0.001）， chemotherapy （χ²=40.41， P<0.001）， oral hygiene （χ²=8.16， P=0.004）， oral pH （χ²=16.83， P<0.001） and oral pathogens （χ²=8.80， P=0.003）. Multivariate analysis showed that， alcohol drinking （OR=2.23， 95%CI： 1.98-6.04， P=0.006）， chemotherapy （OR=3.13， 95%CI： 2.62-6.87， P<0.001） and oral pathogens （OR=3.11， 95%CI： 1.04-9.31， P=0.043） were independent influencing factors for the occurrence of severe radioactive oral mucositis in NPC patients with radiotherapy. Conclusion The oral saliva flow of patients with NPC decreases gradually from the beginning of radiotherapy to the lowest 1 month after radiotherapy and then increases. The pH value gradually decreases from the beginning of radiotherapy to 35 times of radiotherapy， and gradually increases from 1 month to 3 months after radiotherapy. The detection rate of pathogenic bacteria increases rapidly from the beginning of radiotherapy to 15 times of radiotherapy， and the growth rate is stable from 15 times of radiotherapy to 35 times of radiotherapy， and tended to be normal 1 month after radiotherapy. Drinking history， chemotherapy history and oral pathogens are independent risk factors influencing the occurrence of severe radioactive oral mucositis.

Key words: Nasopharyngeal neoplasms, Radiotherapy planning， computer-assisted, Stomatitis, Tumor microenvironment