Gut Health and Breast Cancer Spread: New Findings

A recent study highlights the significant role of gut health in the spread of breast cancer, particularly hormone receptor-positive (HR+) breast cancer. Research conducted by Melanie Rutkowski, Ph.D., at the University of Virginia Comprehensive Cancer Center reveals that bile acids, accumulating due to an unhealthy gut, could facilitate cancer metastasis.

“We found that when the gut microbiome is unbalanced and unhealthy, the control of bile acid levels is lost,” Rutkowski stated. “This disruption creates conditions throughout the body that make it easier for breast tumors to spread.”

HR+ breast cancer is the most prevalent form of metastatic breast cancer. These cancers grow when hormones bind to specific receptors on the cancer cells. According to the Breast Cancer Research Foundation, about 80% of breast cancer cases fall into this category, with approximately 225,000 diagnoses annually in American women.

Metastasis complicates treatment and increases fatality risk. Rutkowski points to the gut’s failure to regulate bile acid composition as contributing to conditions favoring metastasis.

Bile acids, significant signaling molecules, can disrupt metabolism and immune function when imbalanced, leading to cancer cell spread. The study indicates potential strategies to curb metastasis by altering bile acid composition or using bile acid sequestrants, already approved for metabolic diseases.

Audrey Putelo, Ph.D., co-author of the study, emphasizes the potential to develop new approaches for identifying high-risk patients and reducing metastatic disease likelihood. Findings suggest that patients with elevated bile acids and insulin resistance have lower survival rates; however, those receiving bile acid-suppressing drugs often show improved longevity.

Rutkowski describes the results as “extremely encouraging,” voicing hopes that existing FDA-approved drugs can prevent initial cancer spread. Her team is analyzing more patient data to explore long-term effects and understanding immune-related consequences of bile acid signaling.

Further investigation is required to confirm the causal relationship between these medications and improved patient outcomes.

Reference: Putelo, A. M., Bajgai, S., Poblete, M. K., Guido G., Lanfranca, M. P., Rutkowski. M. R.; et al. Commensal Dysbiosis Alters Primary Bile Acid Signaling to Drive Mammary Gland Inflammation and Breast Tumor Dissemination. Cancer Res 2026; https://doi.org/10.1158/0008-5472.CAN-25-4466