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Evaluation of the gut microbiome and sex hormones in postmenopausal women with newly diagnosed hormone receptor-positive breast cancer versus healthy women: a prospective case-control study

M. Kwa, Grant Hussey, Y. Novik, Adrian A. Franke, A. Volkova, Karina Flores, M. J. Blaser, J. Speyer et al.

Journal of Cancer Research and Clinical Oncology, 2025

46 participants · 15 citations

Abstract

The functional composition and diversity of the gut microbiome may affect breast cancer risk by modulation of systemic sex hormones. Gut bacteria with β-glucuronidase enzymatic activity may deconjugate estrogens, leading to increased estrogen reabsorption into the circulation thereby increasing breast cancer risk. We investigated the relationship between the gut bacterial microbiome and endogenous estrogens and related sex hormones in women with hormone receptor-positive breast cancer compared to healthy control women. The goal was to determine if the estrobolome (i.e., bacteria capable of modulating the body’s circulated estrogen levels) was altered in those with breast cancer compared with controls. In this prospective case–control study, postmenopausal women (n = 46) with newly diagnosed stage I-III estrogen and/or progesterone receptor-positive breast cancer were compared with healthy postmenopausal female controls (n = 22). Bacterial composition of the gut microbiome was analyzed by 16S rRNA gene sequencing from fecal specimens. Plasma and urine sex hormones were quantified using high-performance liquid chromatography/mass spectrometry. We found evidence that some β-glucuronidase positive bacteria were enriched in the breast cancer patients compared to healthy controls, whereas abundances of some β-glucuronidase negative bacteria were reduced. There was also a wide distribution of prevalence of β-glucuronidase positive taxa in both breast cancer subjects and healthy…

How strong is the evidence?

Evidence Hub reads this as a case-control, done in people. Its evidence level is 4 of 5 (Low · observational). Observational designs can show an association but not prove cause. Reported size: 46 participants or records.

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