Changes in the microbiome induced by adjuvant chemotherapy for breast and gynecological cancer and their association with weight gain.

Abstract

e22113 Background: Adjuvant chemotherapy for breast cancer is associated with weight gain and glucose intolerance. Obesity increases the risk of cardiovascular morbidity and might increase the risk of disease recurrence. In recent years the role of the intestinal microbiome in human physiology is being uncovered. The microbiome has been shown to influence metabolism and weight gain. We aimed to identify changes in the intestinal microbiome following adjuvant chemotherapy in women and to test their association with weight gain. Methods: Women treated with adjuvant chemotherapy for breast and gynecological malignancies were recruited. Fecal samplesweretaken prior to treatment, after 3-4 cycles and after treatment. Weight was measured atthese time points. Information regarding use of antibiotics and nutritional changes was systematically collected. Gut microbiota was analyzed using 16S rRNA gene sequencing. Results: Fifteen patients were recruited (13 breast cancer, 2 ovarian cancer). 5 gained 1 kg or more during treatment. Antibiotic use was not associated with weight gain. Beta diversity based on uniFrac analysis significantly changed between pre, during and post treatment samples (p = 0.002). Significant increase in the relative abundance of bacterial species from the orders Lactobacillae, Clostridiales, Pasteurellaies and Turicibacterales was seen in samples taken during chemotherapy relative to pre treatment samples. When comparing patients that did and did not gain weight we observed that Ruminococcus bromii was more abundant in pre treatment samples of patients that did not gain weight while other species from the order Clostridiales were more abundant in pre treatment samples of women that did. Alpha diversity decreased during treatment only in patients that gained weight and this difference was of borderline significance (p = 0.07). Conclusions: The composition of the microbiome changed in women during adjuvant chemotherapy for breast and ovarian cancer. We found differences in microbiome content and diversity between patients that gained weight and those that did not. Analyses with a larger sample size are needed to confirm these observations.