The specific combination of bacteria living in a person’s gut can predict the likelihood that melanoma will return after surgery or immunotherapy. Immunotherapy helps immune cells target cancer cells. That’s according to a new study led by researchers at NYU Langone Health and its Perlmutter Cancer Center.
Previous studies have shown that 25% to 40% of melanoma patients experience cancer recurrence despite these two standard approaches, but it has been difficult to predict which patients will experience cancer recurrence.
Magazine published online on April 17th cellA study of 674 patients in a global clinical trial found that differences in the abundance of key bacterial groups (taxa) in the gut predicted cancer recurrence with up to 94% accuracy when patients were analyzed using a new method. The taxa most associated with changes in recurrence risk are: Eubacteria, Ruminococcus, Firmicutesand Clostridium.
“Our study identifies for the first time the types of gut bacteria that serve as markers of increased risk of recurrence in these specific patients, which can help us tailor treatment,” said study lead author Jiyong Ahn, Ph.D., professor in the Department of Population Health at NYU Grossman School of Medicine and associate director of Population Research at NYU Langone Perlmutter Cancer Center.
Current research findings center around the gut microbiome, a group of trillions of bacteria that live in the human gastrointestinal tract. There they train the immune system to distinguish between dangerous bacteria that should be attacked and bacteria that help humans digest food (that should be tolerated). Previous studies have found that study taxa interact with immune cells (such as natural killer cells and T cells) in ways that alter patient responses to immunotherapy. These bacteria can also affect the supply of sugars that fuel cancer cell growth.
geography matters
The new study analyzed gut bacterial species from an international clinical trial called CheckMate 915. Researchers analyzed bacteria in stool samples from melanoma patients whose tumors were surgically removed. Patients from five geographic regions (e.g., North America, Eastern Europe, Western Europe, Australia, and the rest of the world) then received either immunotherapy, nivolumab in combination with ipilimumab, or nivolumab alone.
The research team found that the gut microbiome is a strong predictor of melanoma recurrence, but with a twist. The bacterial marker that most accurately indicates the risk of recurrence depends on where the patient lives.
By first matching patients based on the overall similarity of their gut microbiomes, regardless of where they lived, the researchers were able to find a bacterial “fingerprint” in each region that accurately predicted cancer recurrence. The researchers read the sequence, or order, of the DNA components of all the bacterial species in the patient’s intestines and created a list of which bacterial species were present and absent when the melanoma returned.
Using standard measures of microbial similarity, the research team found that signatures from patients in North America, for example, could accurately predict recurrence in patients in other parts of the world. But that’s only if those patients have similar fingerprints. Levels of these markers were found to predict cancer recurrence with 83 to 94 percent accuracy, depending on geographic region.
“Previous studies were complicated by the fact that the gut bacteria that predict treatment success seemed to vary by region,” Professor Ahn said. “Our study provides a new way to overcome this barrier and shows that these markers are indeed generalizable given a person’s underlying microbiome.”
Finally, the researchers also found that the patients’ gut microbiomes remained remarkably stable over the course of a year of immunotherapy.
“This means that a single pre-treatment microbiome test can be used to reliably predict a patient’s risk,” said study author Richard Hayes, DDS, MPH, PhD, professor in the Department of Population Health at New York University Langone.
The next step is to validate this matching approach in other cancers and build the diverse database needed to make this approach clinically viable. In the future, we envision analyzing a patient’s microbiome before treatment and comparing it to a global database to provide a reliable prognosis to guide treatment from the start. ”
Richard Hayes, Department of Population Health, New York University Grossman School of Medicine
In addition to Ahn and Hayes, study authors from New York University Langone Health included Myhailo Usyk, Huilin Li, Iman Osman, and the late Jeffrey Weber. The authors are Rob Knight and Antonio Gonzalez of the Department of Pediatrics, Computer Science & Engineering, and Bioengineering at the University of California, San Diego.
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New York University Grossman School of Medicine
Reference magazines:
Usyk, M. others. (2026). The gut microbiome is associated with recurrence-free survival in resected high-risk melanoma patients who undergo postoperative adjuvant immune checkpoint blockade. cell. DOI: 10.1016/j.cell.2026.03.041. https://www.cell.com/cell/abstract/S0092-8674(26)00342-9?_returnURL=.
