Prospective evaluation of the fecal microbiome in dogs with large-cell lymphoma receiving chop chemotherapy
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The fecal microbiome composition has been associated with reduced efficacy of cancer therapy and adverse side effects in humans, and chemotherapy has been shown to alter the gut microbiome. The relationship between microbiota and chemotherapy efficacy and tolerability has not been investigated in dogs. We aimed to evaluate changes in fecal microbial diversity during a cycle of CHOP chemotherapy in dogs with lymphoma and whether these changes correlated with adverse events or treatment response. Eighteen dogs with lymphoma were prospectively enrolled, and stool samples were acquired weekly for 6 weeks during CHOP. Fecal samples was analyzed via 16S rRNA amplicon sequencing as previously described. Treatment-associated differences in richness, alpha and beta diversity were determined through comparison to data from healthy controls (n = 26) using factorial ANOVA and PERMANOVA. Dogs with lymphoma had decreased fecal microbial diversity when compared with healthy controls at baseline and throughout treatment (p= 0.0002, 0.0003, 0.0001). Alpha and beta diversity did not significantly change in dogs throughout a cycle of CHOP chemotherapy (p = 0.520 and 0.995). Samples pre-treated with antibiotics were significantly less diverse (alpha and beta diversity) than untreated samples (p = 0.002, 0.0001 respectively). Dogs with lymphoma and fecal samples under the presence of antibiotics had higher levels of Escherchia species in their feces compared to normal dogs. The fecal microbiome of healthy dogs and dogs with lymphoma receiving CHOP is relatively stable over time, but dogs with lymphoma have reduced microbial diversity compared to healthy dogs before and during treatment. An increase in Proteobacteria abundance during treatment may be related to chemotherapy and/or antibiotic use.