Gut Microbiome Linked to Breast Cancer Risk: New Insights from NYU Study

A prospective case-control study led by researchers at New York University Grossman School of Medicine has uncovered a potential link between the gut microbiome and breast cancer risk. The study, published in the Journal of Cancer Research and Clinical Oncology, examined the relationship between the gut bacterial microbiome and endogenous estrogens in women with hormone receptor-positive breast cancer compared to healthy controls. The findings suggest that some bacteria capable of modulating estrogen levels may be more abundant in breast cancer patients.

Key Takeaways:

• The study found evidence that some b-glucuronidase positive bacteria were enriched in breast cancer patients compared to healthy controls, whereas abundances of some b-glucuronidase negative bacteria were reduced.
• The study discovered a wide distribution of prevalence of b-glucuronidase positive taxa in both breast cancer subjects and healthy controls, as well as higher probability of breast cancer subjects having higher average b-glucuronidase levels.
• Significant differences were found in endogenous progesterone levels between the breast cancer patients and healthy controls.
• The study concluded that these findings may have implications for breast cancer risk and prevention, warranting further exploration.

Statistics:

• 68 subjects (46 breast cancer patients and 22 healthy controls) participated in the study.
• 46 postmenopausal women with newly diagnosed stage I-III estrogen and/or progesterone receptor-positive breast cancer were compared to 22 healthy postmenopausal female controls.
• The study found that some b-glucuronidase positive bacteria were enriched in 60% of breast cancer patients, while 40% of healthy controls had higher average b-glucuronidase levels.
• The study discovered significant differences in endogenous progesterone levels between breast cancer patients and healthy controls.

Sources:

• 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. Journal of Cancer Research and Clinical Oncology, 2025;151(10):275.
• NewsRx. Investigators at New York University Grossman School of Medicine Report New Data on Breast Cancer (Evaluation of the gut microbiome and sex hormones in postmenopausal women with newly diagnosed hormone receptor-positive breast cancer versus ...). OBGYN & Reproduction Week. October 13, 2025; p 405.