Health · Medical Research · 1 day ago
Study links gut microbes with cancer outcomes and treatment side effects
Mayo Clinic researchers studied stool samples from 1,364 people with cancer before they began treatment.
The patients came from 40 US states and were treated at Mayo Clinic sites in Arizona, Florida and Minnesota.
The team found that some gut bacteria differed by cancer type, and that younger adults with colorectal or breast cancer had microbial patterns that differed from those of older patients.
These patterns did not appear in the brain cancer patients studied, and the findings do not show that gut bacteria cause cancer.
Comparisons with 287 people without cancer also revealed 341 bacterial species associated with five cancer groups.
Some bacteria were linked to survival in several cancers; for example, Bifidobacterium longum was associated with longer survival in liver and bile duct cancers.
Researchers say further work is needed to find out whether these microbes play a causal role and whether they could guide targeted interventions.
Mayo Clinic researchers linked gut bacteria and bacterial genes with cancer outcomes and chemotherapy side effects.
The study analyzed stool samples from 1,364 cancer patients collected before they began treatment.
Researchers identified 341 bacterial species associated with five cancer groups after accounting for other health conditions.
Younger adults with colorectal cancer had higher levels of lactate and the bacterium Veillonella parvula than patients diagnosed later in life.
The study appeared in Cell and did not establish that the observed microbial patterns cause cancer or its outcomes.
- Who
- Mayo Clinic researchers studied 1,364 patients with cancer and compared them with 287 people without cancer.
- What
- The study linked gut microbes and their genes with cancer groups, survival outcomes and chemotherapy side effects.
- When
- Published October 10, 2026. Patient samples were collected before treatment.
- Where
- Samples came from patients treated at Mayo Clinic in Arizona, Florida and Minnesota; participants represented 40 states.
- Why
- Researchers aimed to identify microbial changes associated with specific cancers and investigate whether the microbiome plays a causal role or could inform targeted interventions.
This story does not have two clearly opposing sides.
We can now narrow the search to those microbial changes that are most specific to individual cancers
Those are the signals we need to understand first if we want to determine whether the microbiome plays a causal role in cancer and ultimately develop targeted interventions.
Patients provided stool samples before beginning treatment at Mayo Clinic.
Researchers linked the samples to clinical records covering diagnoses, treatments, side effects and outcomes.
The study was published in Cell.
- Patient samples
- 1,364 cancer patients
- Comparison group
- 287 people without cancer
- Participants
- Represented 40 states
- Bacterial species
- 341 associated with five cancer groups
- Publication
- Cell, October 10, 2026
Sources
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