Longitudinal changes in gut microbiota composition during endocrine therapy in hormone receptor-positive breast cancer patients.

This prospective study of 90 breast cancer patients examined gut microbiota composition relative to hormone receptor status and endocrine therapy changes. Initial analysis suggested hormone receptor-negative patients had higher Fusobacteriaceae and Fusobacterium abundance, while hormone receptor-positive patients showed Ruminiclostridium enrichment, though differences lacked statistical significance after correction. Hormone receptor-positive patients without lymph node metastasis demonstrated potentially greater microbial diversity, but associations were non-significant after multiple comparison correction. Longitudinal analysis of 52 hormone receptor-positive patients revealed the most robust finding: statistically significant Blautia increases after hormone therapy and aromatase inhibitor treatment. Tamoxifen showed trends toward increased Lachnospiraceae but lost significance after correction due to small sample size. LHRH agonist treatment demonstrated significant Dialister and Megasphaera increases. This study identified limited but robust associations between gut microbiota and endocrine treatments, with Blautia as the most consistently affected genus across multiple therapies, though most findings require validation in larger cohorts.