The Relationship Between Lower Gastrointestinal Tract Reaction Time And Intestinal Flora Composition In Patients With Rectal Cancer During Radiotherapy

Objective:Analyze the composition of intestinal flora in patients with locally advanced rectal cancer before treatment,and explore the influence of different flora composition on the reaction time of lower digestive tract in patients with rectal cancer during radiotherapy.Method:Feces of 30 patients with pre-treatment rectal cancer were collected from December 2017 to June 2018.According to the time of occurrence of lower gastrointestinal reactions during radiotherapy,the patients were divided into non-response group,early response group(lower gastrointestinal reactions occurred within 1-3 weeks of the beginning of radiotherapy),late response group(lower gastrointestinal reactions occurred within 4-6 weeks of the beginning of radiotherapy).The intestinal microorganisms in each group were analyzed.14 cases were eventually enrolled.A standard 16 S rRNA sequence and bioinformatics analysis were performed on 14 stool specimens from rectal cancer patients.To study the effect of different flora composition on the reaction time of lower digestive tract in patients with rectal cancer during radiotherapy.Result:The results of the three groups showed that there was no significant difference in microbial diversity among non-response group,early response group and late response group.From the phylum level,the relative abundance of Bacteroides,Fusobacteria,Lentisphaerae,Cyanobacteria and Verrucomicrobia in the early reaction group was higher than that in the other two groups(P<0.05),and the distribution of Cyanobacteria and Verrucomicrobia in the early reaction group,the late reaction group and the non-reaction group showed a decreasing trend.The relative abundance of Proteus was higher in late reaction group and non-reaction group(P < 0.05).Several species of bacteria that may be associated with radiation damage were further analyzed between groups.The results of subordinate level showed that the richness of Bifidobacterium,Lactobacillus and Anaerotruncus in the non-reaction group was significantly higher than that in the other two groups(P>0.05),which shows the enrichment of these groups may reduce the occurrence of radiation damage.However,there was no significant difference among the three groups of Bacteroides,Streptococcus,Clostridium and Fusobacterium.When species markers were selected between groups,Clostridiceae aggregated in the late reaction group,while Tissierellaceae and Parvimonas aggregated in the non-reaction group.These microflora may be used as biomarkers for the occurrence of lower gastrointestinal tract reactions in the course of radiotherapy.Conclusion:The intestinal flora composition of patients before radiotherapy is different,which may affect the intestinal radiation damage response of patients with locally advanced rectal cancer during radiotherapy.The results showed that the composition of bacterial flora before radiotherapy could predict the occurrence time of lower digestive tract reactions during radiotherapy,which needed to be further validated by enlarging the sample size.It is also suggested that early intervention in bacterial composition may reduce radiation-induced lower gastrointestinal reactions in the future.