Gut Bacteria May Help Predict Heart Risks in Breast Cancer Treatment

Certain gut bacteria were linked to higher risk of heart damage in older patients with breast cancer: © stock.adobe.com.

A healthy gut microbiome before chemotherapy may help protect patients with breast cancer from heart damage, or cardiotoxicity, caused by cancer treatment, according to data shared in a news release from the European Society of Cardiology.

In contrast, researchers found that specific gut bacteria — particularly Bacteroides — were more prevalent in patients with heart health biomarkers, such as left ventricular global longitudinal strain, N-terminal pro b-type natriuretic peptide, and troponin I, that indicate a higher risk of heart damage during cancer treatment. These patients’ gut microbiomes resembled those of individuals with heart failure.

“To allow cancer survivors healthier lives, we need to find new ways to protect them from the long-term side-effects of chemotherapy,” Dr Athos Antoniades said in the news release. “This study is one of the first to ask whether the microbiome could play a role in how well patients’ hearts fare during chemotherapy.”

Antoniades is the head of Research and Development at Stremble Ventures LTD.

“We saw a clear association between some specific genus of gut bacteria and cardiac biomarkers that suggest patients are at greater risk of heart damage during chemotherapy,” he added.

The study included 98 women over the age of 60 with breast cancer from three clinical centers in Europe: The Bank of Cyprus Oncology Centre; the National and Kapodistrian University of Athens, Greece; and the European Institute of Oncology, Italy.

The women underwent ultrasound heart scans, or echocardiograms, to assess heart function and underwent blood tests to check for biomarkers linked to increased risk of heart damage during treatment. Genetic sequencing was used to analyze the bacteria in their gut before they began cancer treatment.

This research is part of the larger, EU-funded CARDIOCARE project, which aims to expand the study to include 600 women to validate the findings. The results suggest that in the future, personalized probiotics could potentially help reduce the risk of heart-related side effects from chemotherapy. The findings are being presented at European Cardio-Oncology 2025, a scientific meeting of the European Society of Cardiology.

“We are already following up these 98 patients after chemotherapy and are expanding the research project to all 600 patients already enrolled in the CARDIOCARE clinical trial.” Antoniades concluded in the news release.

In a separate conversation, CURE spoke with Dr. Vincent Ma to learn more about how the gut microbiome may influence outcomes in melanoma. In the interview, he discussed the findings of the DIET trial, which explored how a high-fiber diet might improve treatment response and reduce side effects in patients receiving immunotherapy.

“Over the years, the gut microbiome may play a very important role in our immune system,” said Ma during the interview.

“We're beginning to learn that the immune system of your gut, the bacteria in your gut, may actually impact how you respond to treatments like immunotherapy.”

Ma is a faculty member in the Division of Hematology, Medical Oncology and Palliative Care, is an assistant professor within the Department of Medicine, and is a faculty affiliate of the Department of Dermatology, all at the University of Wisconsin, School of Medicine and Public Health.

Bacteroidaceae are a common family of gut bacteria that can support health but may become harmful when their populations are imbalanced. In such cases, they can contribute to inflammation and cause infections in other parts of the body.

Heart damage, known as cardiotoxicity, is a relatively frequent side effect of many cancer treatments, including chemotherapy. As breast cancer treatments improve and survival rates increase, more patients are living with the long-term effects of treatment, including damage to the heart.

Reference

1. “Breast cancer patients’ microbiome may hold key to avoiding damaging heart side-effects of cancer therapies,” European Society of Cardiology. News Release. June 20, 2025.

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