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The Hunt for the Perfect Poop: How One Donor’s Microbes Could Transform Cancer Care

In a finding that could reshape cancer care, researchers at Fred Hutchinson Cancer Center have identified what might be called a “super donor” whose gut bacteria show remarkable promise in protecting stem cell transplant patients from life-threatening complications. The discovery emerged from a carefully controlled clinical trial testing fecal microbiota transplantation (FMT) in cancer patients.

The study, published in Nature Communications, found that microbes from one particular donor achieved a 67% engraftment rate in recipients – significantly outperforming other donors and potentially offering a new pathway for preventing graft-versus-host disease (GVHD), a serious complication that affects up to half of stem cell transplant recipients.

The Power of the Right Donor

What made this donor special? The key appears to lie in a bacterial species called Bifidobacterium adolescentis, which was highly abundant (11.6%) in the successful donor’s microbiome but virtually absent in the others. This bacterial species is known for producing beneficial compounds and helping restore gut health after antibiotic treatment.

“The gut microbiome is an organ in itself, and it is connected to the immune system,” explains lead author Armin Rashidi, MD, PhD, a medical oncologist at Fred Hutch. “Since the process of stem cell transplantation damages the gut microbiome, we want to see if FMT will help restore microbial diversity and promote the beneficial bacterial species that support a healthy immune system.”

Safety First

The trial involved 20 patients who received daily oral capsules containing purified microbes for one week. Despite initial concerns about giving live bacteria to immunocompromised patients, the treatment proved remarkably safe. Nineteen of twenty participants completed the week-long treatment, with only mild and temporary digestive symptoms reported.

The impact was striking: none of the eight patients receiving transplants from the optimal donor developed severe GVHD, while all three cases of severe GVHD occurred in patients who received material from a different donor.

The Science Behind the Success

The research team conducted extensive genetic analysis of the microbial communities before and after transplantation. They discovered that patients with less diverse initial gut bacteria actually showed better engraftment of the donor microbes – a finding that could help identify which patients might benefit most from this approach.

Alexander Khoruts, MD, a gastroenterologist at the University of Minnesota Medical School and study coauthor, notes that this represents a new frontier in microbial therapeutics. “Unlike treatment of C. difficile, most indications require optimized formulations of gut microbes. The Fred Hutch trial illustrates this next phase in the development of donor-derived microbial therapeutics.”

Looking Ahead

The findings have launched a larger randomized trial that will enroll 126 patients to definitively test whether FMT from the identified optimal donor can improve outcomes for stem cell transplant recipients. The trial is now actively recruiting at Fred Hutch in Seattle.

“The hope of using FMT with people receiving stem cell transplants is that FMT will help prevent acute GVHD without adding more immunosuppression, improve quality of life, and decrease mortality after transplant,” Rashidi explains.

For the thousands of patients who undergo stem cell transplants each year, this research offers new hope that something as simple as carefully selected beneficial bacteria might help protect them from one of the procedure’s most feared complications.


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