gut bacteria and cancer

A recent study has investigated the effect of an unhealthy gut on the spread of breast cancer.

It is estimated that 1 in 8 women will be diagnosed with breast cancer at some point during their lives. As a result, breast cancer is a growing and major health issue worldwide. Approximately 65% of breast cancers are hormone receptor positive, which means that they are driven by hormones called estrogen and progesterone. However, patients with these types of cancer often have a good prognosis as they often respond well to hormone therapy.

The risk of cancer spreading to other parts of the body – known as metastasis – is associated with clinical characteristics at the time of diagnosis. These include a high number of immune cells called macrophages within the body and increased levels of collagen, which are both associated with an increased risk of breast cancer metastasis.

A recent study carried out at the University of Virginia Cancer Center set out to examine the effects of an unhealthy and inflamed gut on the spread of cancer. During this study, researchers disrupted the gut microbiome of mice using strong antibiotics. In the mice whose gut microbiome was disrupted, the cancer spread.

The results of this study found that an unhealthy gut microbiome increased both the immune cells and collagen. The researchers of this study suggest that an unhealthy microbiome can thus be a predictor of invasion and spread of breast cancer.

The researchers of this study did stress that powerful antibiotics were used to affect the mice’s natural gut microbiota and that the antibiotics used in humans are not dangerous and thus should not be avoided by women with breast cancer. Further research is needed before anyone can outline whether there is a link between chronic antibiotic use and cancer metastasis.

This research adds to the current body of evidence that a healthy microbiome is crucial for many aspects of good health.

Written by Jade Marie Evans, MPharm, Medical Writer


Rosean, C.B. et al 2019. Pre-existing commensal dysbiosis is a host-intrinsic regulator of tissue inflammation and tumor cell dissemination in hormone receptor-positive breast cancer. [Online]. [13 June 2019]. Available from:

Eurekalert . 2019. Unhealthy gut promotes spread of breast cancer, study finds. [Online]. [13 June 2019]. Available from:

Image by Raman Oza from Pixabay

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