A high-fiber diet leading to higher gut microbiome diversity may improve response to anti-PD-1 immunotherapy in patients with melanoma, according to the results of a new study presented at the 2019 American Association for Cancer Research Annual Meeting in Atlanta, GA. 

Researchers studied fecal samples from 113 patients with melanoma to characterize the diversity and type of bacterial species in each patient’s gut microbiome. They found that higher microbiome diversity was associated with greater response to therapy regardless of treatment type, but for anti-PD-1 immunotherapy specifically, patients were five times more likely to respond to treatment.

The link was specifically for a high-fiber diet leading to more gut microbiome diversity, not for supplementing with probiotics. In fact, the 40% of patients in the study who reported use of probiotic supplements had lower gut microbiome diversity. 

The researchers noted that this is the first clinical study to report results on the relationship between diet, microbiome, and checkpoint blockade immunotherapy response.