Gut Microbiome and Symptom Burden in Obese and Non-Obese Women Receiving Chemotherapy for Breast Cancer

Purpose: Obese women with breast cancer experience high symptom burden, poor quality of life, and increased mortality compared to non-obese women with breast cancer. Obesity-related changes to the bacteria of the gut, the GI microbiome, may be one such mechanism for these differences in outcomes. The purpose of this work is to report symptom burden and GI microbiome composition between obese and non-obese women with breast cancer to identify potential microbial influences for symptom severity. Methods: 59 women with breast cancer (26 obese, 33 non-obese) provided symptom reports using the Memorial Symptom Assessment Scale and stool samples for 16S analysis one week after receiving chemotherapy. Symptom reports were summarized and examined for differences based on obesity. Fecal microbiome analysis was compared between groups using alpha-diversity (Shannon index), beta-diversity (Principal Coordinate Analysis with weighted UniFrac distances), and LASSO analysis of abundance of bacterial species. Results: While symptom burden was high, it did not differ based on obesity status. Alpha- and beta-diversity did not find significant differences based on obesity, but LASSO analysis identified eight bacteria to be significantly enriched in obese participants: Collinsella aerofacien, Prevotella 7, Coprobacillus cateniformis, Ruminococcus torques group, Agathobacter, Frisingicoccus, Roseburia inulinivorans, and Monoglobus pectinilyticus. Conclusions: Identifying biologic mechanisms driving symptoms is necessary for the development of therapies to reduce cancer-related symptom burden. While obesity may alter the GI microbiome and influence symptom burden in women with breast cancer, these effects may be outweighed by the effects of chemotherapy on the gut.