This week, two studies offer a raft of evidence from cancer patients suggesting that the gut microbiome—the community of bacteria, viruses, and other bugs living in our digestive tracts—helps determine whether tumors shrink when treated with a powerful new type of cancer drug. Patients who took antibiotics for routine reasons before or soon after starting a type of immunotherapy known as a PD-1 inhibitor relapsed and died sooner than those who were antibiotic-free. And when mice received fecal transplants from patients who responded to the drugs, they did better on PD-1 blockers than did mice given nonresponder feces. Researchers are now planning a clinical trial to test whether manipulating the gut microbiome could help more cancer patients respond to PD-1 blockers.
