Introduction

Reduced fecal microbial diversity has been associated with cancer development, treatment response and treatment tolerability through its interaction with the gastrointestinal tract and the immune system in humans. Assessing the fecal microbiome may be a useful tool for helping predict treatment outcomes and side effect profiles in dogs with cancer. We aimed to evaluate changes in fecal microbial diversity after a single dose of doxorubicin chemotherapy and correlate these changes with clinical parameters.

Methods

Fifteen dogs with spontaneously-occurring cancer were prospectively enrolled, and stool samples were collected on days 0, 4, 7 and 21 after doxorubicin chemotherapy. The fecal microbiome was analyzed via 16S rRNA amplicon sequencing as previously described. Treatment-induced differences in alpha and beta diversity were determined through comparison to data from healthy controls (n=27) using a repeated measures ANOVA and PERMANOVA.

Results

Dogs with cancer receiving doxorubicin had decreased fecal microbial diversity when compared with healthy controls at baseline and at all study time points (p=0.0007, 0.001, 0.0001, 0.0006). Alpha and beta diversity did not significantly change in dogs throughout a cycle of doxorubicin (p=0.194 and 0.371). Samples pre-treated with antibiotics were significantly less diverse (alpha and beta diversity) than untreated samples (p=0.0504, 0.006 respectively). Gastrointestinal signs were not associated with significant changes to the fecal microbiome during treatment.

Conclusion

The fecal microbiome of healthy dogs and dogs with cancer receiving doxorubicin chemotherapy is relatively stable over time, but dogs with cancer and those receiving antibiotics have reduced microbial diversity compared to healthy dogs.

Funding Information

This study was funded by a 2019 VCS Resident Grant