A healthy gut microbiome before chemotherapy protects breast cancer patients from cardiotoxicity

New research shows that a healthy microbiome before chemotherapy may help protect breast cancer patients from heart damage, or cardiotoxicity, resulting from cancer treatment.

Researchers found that certain bacteria in the gut microbiome of patients are associated with biomarkers of heart health, and their deficiency or excess indicates a higher risk of heart damage during chemotherapy.

“To enable cancer survivors to lead healthier lives, we need to find new ways to protect them from the long-term side effects of chemotherapy. This study is one of the first to ask whether the microbiome plays a role in how well a patient’s heart tolerates chemotherapy,” explained Dr. Athos Antoniades, head of research and development at Stremble Ventures LTD, who leads multiomics projects, including gut microbiome DNA sequencing.

“We saw a clear link between certain specific types of gut bacteria and cardiac biomarkers that indicate that patients are at greater risk of heart damage during chemotherapy,” he added.

Although further research is needed, this gives us hope that in the future, individually tailored probiotics could play an important role in protecting patients from the harmful effects of cancer treatment.

The study involved 98 women over the age of 60 diagnosed with breast cancer from three clinical treatment centers across Europe: the Cyprus Cancer Center, Cyprus; the National and Kapodistrian University of Athens and the Hellenic and European Institute of Oncology, Italy.

The women underwent an ultrasound scan of the heart, also known as echocardiography, to check heart function, and blood tests were performed to determine biomarkers known to increase the risk of heart damage in women during treatment. Genetic sequencing was used to profile all the bacteria in the patients’ intestines before cancer treatment began.

This study is part of a larger project called CARDIOCARE, which will expand the study to 600 women to confirm the results. The findings offer hope that in the future, individually tailored probiotics could be used to protect women from the side effects of chemotherapy on the heart.

The researchers found that certain bacteria, called Bacteroides, were prevalent in patients who also had biomarkers of heart health, specifically LV¬GLS, NTproBNP, and troponin I, which indicate that patients are more susceptible to heart damage during cancer treatment. The gut bacteria profile of these patients was similar to that of patients with heart failure.

Bacteroidaceae is a family of very common gut bacteria that can be beneficial to health, but can also be harmful when their numbers are disrupted. They can cause infections in other parts of the body and contribute to inflammation.

Heart damage, or cardiotoxicity, is a relatively common side effect of many cancer treatments, including chemotherapy. As breast cancer treatments improve and more patients recover, more patients are living with the long-term side effects of treatment.

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Published: 20.06.2025

Updated: 22.06.2025

Medical author, Medical editor:

Stepan Yuk

Medical expert:

PhD. Olexandr Voznyak