Bowel cancer patients will be given a ground-breaking treatment which alters the makeup of their gut bacteria in a trial launching this year.

Led by an international team, the phase one trial will investigate whether gut bacteria contribute to triggering cancer as well as whether they make the disease more resistant to treatment in some patients.

Gut bacteria - the microbiome

The trillions of bacteria found in the human gut play a crucial role in digesting food and strengthening the immune system. Emerging evidence suggests that certain strains of bacteria may be involved in triggering cancer by allowing it to develop unchecked or by making cancers resistant to chemotherapy.

Professor Wendy Garrett, of the Harvard TH Chan School of Public Health, is co-leading the project and said that treatments to reset or alter the microbiome could be used alongside conventional cancer drugs in the future.

Everybody involved in this project wants to improve outcomes for patients with bowel cancer and, ultimately, we want to prevent it.

The initial trial will involve a dozen patients and will investigate the potential for using faecal transplants to reset the gut of patients by reducing the presence of cancer-associated microbes.

The procedure will involve transplanting a stool sample containing microbes from a healthy donor.

Gut bacteria is different in bowel cancer patients

Previous studies by Garrett and the projects other co-leader, Professor Matthew Meyerson, revealed that gut bacteria varies in bowel cancer patients. A microbe called Fusobacterium nucleatum was more common in cancerous tissue and in cancer patients than in healthy people.

In this study, when mice that were predisposed to developing cancer were exposed to this bacteria, tumours occurred more quickly. Thus, Garrett suggests,

Maybe this bacterium has a role enabling bowel cancer or taking the brakes off bowel cancer development.

One theory under investigation is that the bacterium sticks to pre-cancerous cells, shielding them from being spotted by the immune system creating the opportunity for them to spiral into a cancerous state.

Studies have also suggested that so-called good bacteria are more common in patients who respond to chemotherapy and other cancer treatments.

Lifestyle affects gut bacteria

A range of lifestyle factors are linked to a person’s risk of developing bowel cancer, including diet and obesity. Meyerson says the study will look at whether changed in gut bacteria are linked to these lifestyle factors.

Maybe this is going to be incredibly important for the understanding and treatment and prevention of bowel cancer. Maybe it’s just going to be a phenomenon that’s there. Until we answer a lot of questions, we won’t know.

The project will also look into other potential treatments such as antibiotics and vaccines which could trigger an immune reaction against targeted microbial communities in the gut.

Currently the best chance we have of surviving bowel cancer is catching early when surgery can be most effective.