DISCUSSION
tumor, NPC, cancer, toxicity, pain, bone marrow suppression, weight loss
TUMOR, ORAL MUCOSITIS, PRIMARY TUMOR, CANCER, DISEASES, DISEASE, BONE MARROW SUPPRESSION, ADVERSE EFFECTS, CAVITY, ULCERATION, REGRESSION, PATHOGENESIS
In clinical practice, the vast majority of NPC patients would experience varying degrees of oral mucositis during radiotherapy, and the incidence of severe radiation‐induced oral mucositis ranges from 20% to 40%.The pathogenesis of oral mucositis resulting from concurrent chemo‐radiotherapy is mainly divided into five stages, namely, initiation, upregulation/activation, signal amplification, ulceration, and healing stages.Due to the rotation of the earth, organisms constantly cycle during daytime and nighttime, and most of them have their circadian rhythms, which regulate the body's physiological and metabolic processes to adapt to different times in the day.In this study, based on the cycle of oral mucosal cells, radiotherapy was scheduled in the corresponding time window of the cell cycle according to the different cycle distribution patterns of oral mucosal cells in a day, to explore a new method to reduce radiation‐induced oral mucositis in NPC patients. We found that Grade 2 and 3 oral mucositis caused by radiotherapy at noon (11:30 ~ 15:30) was milder than that caused by radiotherapy at night (19:00 ~ 23:00), and the occurrence time of Grade 2 oral mucositis after radiotherapy conducted at noon was also delayed compared with radiotherapy conducted at night. We also found that the incidence of Grade 2 oral pain caused by radiotherapy conducted at noon was milder than that caused by radiotherapy conducted at night. There was no significant difference in the short‐term efficacy of tumor regression between the day group and night group, nor in the degree of bone marrow suppression or weight loss during treatment.Bjarnason et al.Fang Yi et al.In addition, the cases in previous studies include a variety of diseases, and the anatomical location of the primary tumor is different, which may affect the reliability of the research conclusions. With sufficient disease sources, Guangxi, China is of a high incidence of NPC. In our study, NPC was studied by separately selecting the relatively fixed locations of the primary tumor and relatively the same exposure dose to the oral cavity. At the same time, it was analyzed when there was no significant difference in the exposure dose to the oral cavity between the two groups, so the correlation between radiation‐induced oral mucositis and radiotherapy time window in NPC patients was demonstrated in a comparably better manner.Oral pain score is generally related to the severity of oral mucositis.Previous studies have shown that weight loss due to radiotherapy has adverse effects on the prognosis of NPC patients.Since bone marrow suppression was mainly caused by chemotherapy and there was no significant difference in the number of patients undergoing concurrent chemotherapy between the two groups, there was no significant difference in the degree of bone marrow suppression between the two groups.At the same time, we also compared the tumor regression between the two groups, and there was no significant statistical difference in this regard in the two groups, either. This indicates that radiotherapy at the different time points of the cycle of oral mucosal epithelial cells does not affect the short‐term efficacy of cancer treatment.This study has several limitations. Due to time constraints, we included a small number of cases. Also, due to machine failure, working system, and staffing, we could not ensure that all radiotherapy operations for the patients were scheduled within the predetermined period, but have ensured that over 90% of radiotherapy operations for all the patients were conducted within the predetermined period. We will also count the differences in the relapse rate and overall survival rate of patients between the two groups in the future. In addition, the duration and recovery time of oral mucositis of patients after radiotherapy were not further tracked, therefore, they need to be further explored in future studies.In summary, our results suggest that by scheduling radiotherapy based on the corresponding time window of the cycle of oral mucosal cells, the severity of oral mucositis and oral pain was reduced in NPC patients during radiotherapy. It neither affected the efficacy nor increase treatment toxicity. Therefore, this radiotherapy mode might be an effective way to reduce radiation‐induced oral mucositis but not increase the cost in NPC patients.