Researchers from NYU Langone Health have found that the mix of bacteria in a melanoma patient’s gut can predict cancer recurrence with up to 94 percent accuracy, but only when analyzed according to the patient’s geographic region.
The study, published April 17 in the journal Cell, analyzed stool samples from 674 melanoma patients enrolled in the international CheckMate 915 clinical trial. These patients had undergone tumor removal and were treated with either nivolumab alone or in combination with ipilimumab.
Past research shows that 25 to 40 percent of melanoma patients experience recurrence despite surgery and immunotherapy, making prediction a critical gap in care. The new findings address this by identifying specific bacterial groups — Eubacterium, Ruminococcus, Firmicutes, and Clostridium — whose abundance correlates with recurrence risk.
However, the predictive power of these microbes is not uniform. The bacterial signatures most strongly linked to recurrence varied across North America, Eastern Europe, Western Europe, Australia, and other regions.
To overcome this, researchers first grouped patients by overall gut microbiome similarity, regardless of location. Within these clusters, they identified region-specific bacterial “fingerprints” that accurately forecasted relapse.
A signature derived from North American patients, for example, could predict recurrence in patients elsewhere — but only if those patients shared a similar microbial profile.
For more on this story, see Can Your Housemates Change Your Gut Bacteria?.
“Our study identified for the first time gut bacterial types that can serve as markers of increased recurrence risk in these specific patients, which will help tailor treatment,” said senior author Jiyoung Ahn, PhD, professor of population health at NYU Grossman School of Medicine and associate director of population research at Perlmutter Cancer Center.
The gut microbiome trains the immune system to distinguish harmful from helpful bacteria. The taxa studied interact with immune cells such as natural killer cells and T cells, influencing response to immunotherapy. They may also affect sugar availability that fuels cancer cell growth.
These findings suggest that future melanoma follow-up could include stool testing to guide decisions about additional therapy or surveillance intensity. However, implementing such tests would require standardized, region-specific reference databases.
This follows our earlier report, Kimchi & Onions: Gut Bacteria Fight Nanoplastics & Boost Muscle Strength.
The research underscores the growing role of the microbiome in cancer outcomes but highlights the challenge of translating microbial signatures into broadly applicable clinical tools.
Can gut bacteria testing predict melanoma recurrence for all patients?
No. The study found that bacterial predictors of recurrence are region-specific. A model accurate for North American patients may not function for others unless their gut microbiomes are similar.
What treatments were patients receiving in the study?
Patients received either nivolumab alone or nivolumab combined with ipilimumab after surgical removal of melanoma tumors.