In a small study, 12 people with advanced cancer that had stopped responding to a type of immunotherapy got a treatment that transplants gut bacteria along with the immunotherapy. The treatment did not shrink any tumors in any patient, though 5 patients had their cancer stay the same and 7 saw their cancer grow.
See the scientific wording
Fecal microbiota transplantation combined with immune checkpoint inhibitors produced no objective tumor responses (0 of 12 patients) in a single-arm phase IIa trial involving 12 patients with advanced cancers resistant to immune checkpoint inhibitors; 5 patients achieved stable disease and 7 experienced disease progression.
Correlational — new studies may shift this
ObservationalOne moderate-quality study links this claim to the outcome, but causation is not established.
What the research says
1 study reviewedSupporting (1)
Cohort StudyHuman2026
The study's results exactly match what the claim says: none of the 12 patients had their tumors shrink, while 5 had their cancer stay the same and 7 had it grow.
Contradicting (0)
No contradicting studies found yet
That doesn't mean it's settled — it just means no study has tested the opposite.
Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.
Scores reflect study quality, not just count.
Doctors gave patients a treatment that puts healthy gut bacteria from other people into their stomachs. They hoped this would wake up the immune system to attack cancer. But even though the bacteria settled in the gut, the immune system stayed sleepy, with too many cells that calm it down and not enough fighters. So the cancer kept growing.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting study
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In a small study, 12 people with advanced cancer that had stopped responding to a type of immunotherapy got a treatment that transplants gut bacteria along with the immunotherapy. The treatment did not shrink any tumors in any patient, though 5 patients had their cancer stay the same and 7 saw their cancer grow.
Mechanism
1 studyThe treatment with healthy gut bacteria didn't work because it didn't change the patient's immune system in the right way. The immune system stayed in a state that lets the cancer grow, with too many 'calming' cells and not enough 'attacking' cells. So the tumors kept growing.
Doctors gave patients a treatment that puts healthy gut bacteria from other people into their stomachs. They hoped this would wake up the immune system to attack cancer. But even though the bacteria settled in the gut, the immune system stayed sleepy, with too many cells that calm it down and not enough fighters. So the cancer kept growing.
Fecal material from healthy donors is introduced into the patient's intestine, leading to temporary colonization by donor bacteria.
The altered gut bacteria are supposed to send signals to the immune system, prompting it to activate T cells that can attack tumor cells.
In this patient group, the immune system does not respond as hoped. Instead of increasing activated T cells, the body produces more immunosuppressive cells (CD14+ monocytes) and inflammatory signals (IL-8), which suppress anti-tumor immune activity.
Because the immune system remains suppressed, tumor cells continue to grow, and no tumor shrinkage occurs.
Evidence from Studies
Supporting (1)
Community contributions welcome
The study's results exactly match what the claim says: none of the 12 patients had their tumors shrink, while 5 had their cancer stay the same and 7 had it grow.
Contradicting (0)
Community contributions welcome
Score Breakdown
No multi-axis breakdown available yet. The overall Pro / Against score above is the best signal.
- No clinical evidence is available; the score reflects mechanistic plausibility only.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Systematic Review and Meta-Analysis of Randomized Controlled Trials Evaluating Fecal Microbiota Transplantation Combined with Immune Checkpoint Inhibitors in Advanced Cancers Resistant to Checkpoint Inhibitors
Comprehensive search of databases for RCTs comparing FMT+ICIs vs control (ICI alone or placebo) in patients with ICI-resistant advanced solid tumors; meta-analyze objective response rates, progression-free survival, overall survival.
Double-Blind, Randomized, Placebo-Controlled Trial of Fecal Microbiota Transplantation Combined with Immune Checkpoint Inhibitors in Patients with Advanced Cancers Resistant to Immune Checkpoint Inhibitors
Randomized, double-blind, placebo-controlled trial with 2 arms: FMT+ICI vs placebo+ICI; stratified by cancer type and prior lines of therapy; primary endpoint objective response rate by RECIST 1.1, secondary endpoints progression-free survival and overall survival; adequate sample size to detect a clinically meaningful difference.
Prospective Cohort Study of Fecal Microbiota Transplantation Combined with Immune Checkpoint Inhibitors in Patients with Advanced Checkpoint-Inhibitor-Resistant Cancers
Enroll patients with ICI-resistant advanced cancers who will receive FMT+ICIs; collect clinical and microbiome data; follow for response (RECIST), progression-free survival, overall survival; compare with historical controls or propensity-matched patients receiving ICI alone.
Case Series of 12 Patients with Advanced Checkpoint-Inhibitor-Resistant Cancers Treated with Fecal Microbiota Transplantation and Immune Checkpoint Inhibitors: Detailed Clinical Outcomes
Detailed clinical histories, imaging, and microbiome analyses of each patient; document response, stable disease, progression, adverse events.