A small clinical trial shows that faecal microbiota transplants can improve outcomes for kidney cancer patients on immunotherapy drugs. Participants receiving transplants experienced longer cancer stability and greater tumor shrinkage compared to those given placebos. The approach targets the gut microbiome to boost immune responses against tumors.
Researchers have found promising evidence that faecal microbiota transplantation (FMT) could augment cancer treatments by modifying the gut microbiome. In a trial involving 45 adults with kidney cancer, participants had recently begun treatment with the checkpoint inhibitor pembrolizumab and axitinib, which starves tumors of blood supply. They were randomly assigned to receive either FMT from a donor who achieved cancer remission via checkpoint inhibitors or a saline placebo, administered initially through a tube into the large intestine. Three and six months later, most received two additional doses as oral pills. On average, cancer remained stable for two years in the FMT group, versus nine months in the placebo group. Moreover, over half of FMT recipients saw their tumors shrink, compared to about one-third in the placebo group. Gianluca Ianiro at the Catholic University of the Sacred Heart in Rome, Italy, explained: “The microbiome is a strong regulator of host immunity, so we hypothesise that altering it can boost immunity to help kill cancer.” Analysis of stool samples revealed that FMT introduced Blautia wexlerae, a bacterium producing short-chain fatty acids that support anti-cancer immune cells. It also lowered levels of inflammatory Escherichia coli and increased Ruminococcus bromii, which fosters beneficial bacteria. Hassane Zarour at the University of Pittsburgh noted: “This meaningfully strengthens the evidence that the gut microbiome can be therapeutically manipulated to influence immunotherapy outcomes.” A separate trial this week demonstrated similar benefits for non-small cell lung cancer patients. Experts like Arielle Elkrief at the University of Montreal suggest potential applications to other checkpoint inhibitor-responsive cancers, such as those in the bladder and head and neck, but larger randomized controlled trials are essential. Further studies aim to identify key bacterial strains for scalable artificial treatments. The findings appear in Nature Medicine (DOI: 10.1038/s41591-025-04189-2).
