RESUMO
PURPOSE: To investigate relationships between body size, gut microbiome, and health-related quality of life (QOL) in breast cancer survivors (BCS) in a clinical trial. METHODS: A cross-sectional substudy was conducted using baseline data from 70 BCS participating in a randomized controlled trial of a lifestyle intervention. Measures included anthropometrics, QOL (Short Form Health-related QOL Survey-36 [SF-36]), and 16S rRNA gene sequencing of fecal microbes. Participants were categorized by body mass index (BMI) into without obesity (≤ 29.9 kg/m2; n = 38) and with obesity (≥ 30.0 kg/m2; n = 32) groups. Differences in bacterial taxa between groups were assessed using Kruskal-Wallis one-way analysis of variance. Spearman and partial correlations explored associations between taxa and SF-36 subscales. Mediation analysis explored the relationship between BMI and SF-36 mental health summary score with alpha diversity as a mediator. RESULTS: Most BCS (72.9%) were non-Hispanic White with average age of 61.6 (± 8.7) years. No differences were observed for SF-36 subscales between groups. Physical functioning, vitality, and mental health subscales were negatively associated with Ruminococcus (ρ = - 0.304, p = 0.036; ρ = - 0.361, p = 0.012; ρ = - 0.495, p < 0.001) and Dorea (ρ = - 0.378, p = 0.028; ρ = - 0.33, p = 0.022; ρ = - 0.388, p = 0.006) abundance controlling for BMI. BCS without obesity had a significantly higher relative abundance of Ruminococcus (p = 0.003), Streptococcus (p = 0.049), Roseburia (p = 0.035), and Dorea (p = 0.003). CONCLUSIONS: Fecal microbial composition differed between BCS with and without obesity, with associations between QOL and several microbial taxa. Several of these genera, previously identified as potentially beneficial, may also influence QOL in BCS. These results support further studies to determine the role of individual microbiota in QOL and obesity in cancer survivors.