Gut microbiome in association with chemotherapy-induced toxicities among patients with breast cancer

Background: Little research has focused on the relationship between gut microbiome and chemotherapy-induced toxicity. Methods: This prospective study involves 301 patients with breast cancer who had prechemotherapy stool samples collected. Gut microbiome was sequenced by shotgun metagenomics; associations with chemotherapy-induced toxicities during first-line treatment by gut microbial diversity, composition, and metabolic pathways with severe (i.e., grade >= 3) hematological and gastrointestinal toxicities were evaluated via multivariable logistic regression. Results: High prechemotherapy alpha-diversity was associated with a significantly reduced risk of both severe hematological toxicity (odds ratio [OR] = 0.94; 95% CI, 0.89-0.99; p = .048) and neutropenia (OR = 0.94; 95% CI, 0.89-0.99; p = .016). A high abundance of phylum Synergistota, class Synergistia, and order Synergistales were significantly associated with a reduced risk of severe neutropenia; conversely, enrichment of phylum Firmicutes C, class Negativicutes, phylum Firmicutes I, and class Bacilli A, order Paenibacillales were significantly associated with an increased risk of severe neutropenia (p range: 0.012-2.32 x 10(-3); false discovery rate <0.1). Significant positive associations were also observed between severe nausea/vomiting and high Chao1 indexes, beta-diversity (p < .05), 20 species belonging to the family Lachnospiraceae, Oscillospiraceae, and Ruminococcaceae (p value range: 6.14 x 10(-3) to 1.33 x 10(-5); false discovery rate <0.1), and three metabolic pathways involved in reductive tricarboxylic acid cycle I and cycle II, and an incomplete reductive tricarboxylic acid cycle (p < .01). Conversely, a high abundance of species Odoribacter laneus and the pathway related to the L-proline biosynthesis II were inversely associated with severe nausea/vomiting. Conclusions: Our study suggests that gut microbiota may be a potential preventive target to reduce chemotherapy-induced toxicity.