Chemoradiotherapy-driven Intestinal Microbial Dysbiosis Contributes To The Variation In Its Side Effects

ObjectiveTo study the dynamic changes of intestinal microbial composition during and after concurrent chemoradiotherapy in the patients with colorectal cancer;and the correlation of chemoradiotherapy-related side effects with the intestinal bacterial dysbiosis.Subjects and MethodsNineteen patients with colorectal cancer in the Department of Radiotherapy,the First Hospital of Jilin University between June 2018 and June 2019 were recruited.During concurrent chemoradiotherapy,the fecal samples were collected,and chemoradiotherapy-related side effects were accessed.In this study,the patients were required to sign informed consent.1.The intestinal bacterial DNA was isolated;the V3-V4 region of bacterial 16S rDNA was amplified and sequenced by Illumina Miseq platform.2.DESeq is used to select the different abundant bacteria,and diversity indexes were also calculated.3.“Common Terminology Criteria for Adverse Events(CTCAE)Version 4.0 1”was used to assess the severity of side effects.4.Random forest-regression method was used to determine the correlation of the side effect severity after chemoradiation with the intestinal microbiota,and whose bacteria played a critical role in the relationship with side effects.5.The“two-part regression model”was constructed to determine the correlation between the intestinal microbiota and side effects.Results110 final fecal samples were collected,the average number of sequences per sample was 13,428,and the effective sequencing-depth was 250.0 bp.Using Qiime dada2,Qiime Vsearch and the public microbiol database“Greengene”,the sequences with similarity greater than 97%were clustered to obtain a total of 1,042 operational classification units(OTUs).These OTUs were aligned to 418 taxa.The rarefaction curve tended to be flat while the sequencing-depth reached 4,000 bp.1.The number of OTUs and Shannon index of intestinal microbiota significantly decreased at the 20th chemoradiotherapy compared with the 10th chemoradiotherapy(observed species,FDR-corrected P=0.502;Shannon index,FDR-corrected P=0.284).The principal component analysis showed that the microbiol composition at the 20th chemoradiotherapy was significantly different from that at 5th chemoradiotherapy(weighed UniFrac distance metric:R~2=0.03,FDR-corrected P=0.405);and the microbiol composition at 15th chemoradiation was significantly different from that at the end of chemoradiotherapy(unweighted UniFrac distance metric:R~2=0.03,FDR-corrected P=0.402).2.DESeq showed that at the genus level,the fecal samples collected after chemoradiotherapy exhibited significant decreases in abundances of Mycobacterium,Mycobacterium,Papillibacter and Anaerotruncus(>4 times,FDR-corrected P<0.05),Lactobacillus,Odoribacter and Peptostreptococcus(>8 times,FDR-corrected P<0.05);while the abundances of Coprococcus,Rothia,Parabacteroides,Bacillus,Weissella and Prevotella(>4 times,FDR-corrected P<0.05),Alkanindiges,Actinomyces and Selenomonas(>8 times,FDR-corrected P<0.05)increased significantly.At the phylum level,the fecal samples collected after chemotherapy exhibited significant increases in the abundances of Cyanobacteria and TM7(>8 times,FDR-corrected P<0.05);while the abundances of Synergistetes(>4 times,FDR-corrected P<0.05)decreased significantly.3.Random forest-regression method was used to obtain 28 side effect-related microbiol biomarkers.In this model,the intestinal microbiota can explain 5.63%of the variation in the side effects(P<0.05).The microbiol biomarkers included Peptostreptococcus,Anaerosinus,and Parabacteroides.4.In the“two-part regression model”,32 bacterial taxa were determined to be associated with the side effects,of which 7 came from the quantitative analysis model,9 from the binary analysis model,and 16 from qualitative-binary combined meta-analysis model.The intestinal microbiota could explain 6.74%of the variation in the side effects(P<0.05).ConclusionConcurrent chemoradiotherapy changes the intestinal microbiol composition of the patients with colorectal cancer,leading to intestinal microbiol dysbiosis.The intestinal microbiol dysbiosis is associated with chemoradiotherapy-related side effects.The intestinal microbiota as a whole can explain 9.74%of the variation in the side effects.