Plate Nº 25 · recorded October 10, 2026
Health & Medicine ResearchReported finding
Mayo Clinic Study Maps Gut Microbes Across 1,364 Cancer Patients
Mayo Clinic researchers analyzed stool samples from 1,364 cancer patients, identifying 341 bacterial species tied to five cancer types and distinct patterns in early-onset colorectal and breast cancers.
By Marcus Bennett3 min read636 words
In brief
- Researchers analyzed stool samples from 1,364 cancer patients across 40 U.S. states, compared with 287 people without cancer
- They identified 341 bacterial species associated with five cancer groups
- Colorectal cancer incidence is rising about 3% per year among adults ages 20 to 49
- Breast cancer incidence is rising 1.4% per year among women under 50
- Bifidobacterium longum was linked to longer survival in liver and bile duct cancer patients
Mayo Clinic researchers analyzed stool samples from 1,364 cancer patients treated at sites in Arizona, Florida and Minnesota, identifying 341 bacterial species linked to five cancer groups. The study, published in Cell, also found that adults 50 and younger with colorectal and breast cancers carry distinct gut microbiome patterns compared with patients diagnosed later in life.
What microbiome differences did researchers find in early-onset cancers?
The team compared stool samples collected before treatment began, pairing each sample with detailed clinical records on side effects and outcomes. Patients came from 40 U.S. states.
In younger patients with colorectal cancer, samples carried higher lactate levels and more Veillonella parvula, a bacterium that feeds on lactate. Tumors can produce large amounts of lactate, raising a question about whether this fuel feeds V. parvula in ways that contribute to early-onset disease.
Early-onset breast cancer showed broader shifts. Researchers found changes across 64 bacterial species, with lower levels of primary bile acids. One of those species, Clostridium scindens, plays a role in bile acid and steroid metabolism.
Brain cancer, the third cancer examined in the age comparison, showed no comparable age-related microbiome differences.
Which cancer types showed the strongest signals?
Researchers first compared 1,364 cancer patients with 287 people without cancer, then narrowed the search for cancer-specific patterns.
- Neuroendocrine tumors: broad loss of common health-associated gut bacteria
- Liver and intrahepatic bile duct cancers: higher levels of several bacteria, including Enterococcus faecalis
- Esophageal cancer: higher levels of six species, including Streptococcus bacteria
- Lymphoid leukemia, multiple myeloma and related cancers: distinct links
"We can now narrow the search to those microbial changes that are most specific to individual cancers," said co-corresponding author Ruben Mars, Ph.D., a microbiome researcher at Mayo Clinic in Minnesota. "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."
Could gut bacteria predict treatment side effects?
The team asked whether the pre-treatment gut microbiome could flag patients at risk of chemotherapy-induced diarrhea, a side effect that often complicates care.
Among patients receiving 5-fluorouracil (5-FU), those who later developed diarrhea had lower levels of bacterial genes capable of breaking down the drug. Most of that function came from Anaerostipes hadrus, a common gut bacterium.
The same signal did not appear in patients receiving carboplatin, a different chemotherapy drug, suggesting the finding is specific to 5-FU rather than chemotherapy in general.
Does the microbiome track with survival?
Researchers identified bacteria linked to survival in five cancer types: colorectal, liver and intrahepatic bile duct, ovarian, prostate, and melanoma.
In liver and bile duct cancer:
- Bifidobacterium longum: associated with longer survival
- Blautia A massiliensis: associated with shorter survival
What remains unknown?
The findings do not establish that microbial or metabolic differences cause early-onset disease, only that they correlate with it.
Cancer rates are climbing among younger adults. Colorectal cancer incidence is rising about 3% a year among adults ages 20 to 49, and breast cancer incidence is rising 1.4% a year among women under 50, according to the American Cancer Society.
"The microbiome is not the sole driver of cancer or treatment outcomes, but it is an underappreciated component that has not traditionally been considered in therapeutic approaches," said co-corresponding author Purna Kashyap, M.B.B.S., director of the Mayo Clinic Microbiome Program.
"This gives us a proof of concept that we can begin to understand why some patients experience a particular side effect and identify a target that could potentially be acted upon."
Next, the team plans to test whether cancer-specific microbial signals play a causal role in disease and to validate microbiome-based predictions of treatment side effects in larger patient groups.
via Medical Xpress (Source)
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