A fecal transplant is when a doctor takes a sample of fecal matter from a donor and inserts it into the intestines of a patient, usually via colonoscope. It’s primarily used to treat bacterial infections, by introducing “good” bacteria into the colon and balancing the GI tract’s microbiome. But we may have found a new use for the treatment.

A study published this month in Nature Medicine has found that fecal transplants are effective in fighting colon cancer when used alongside immunotherapy. Instead of being inserted via colonoscope, participants took the fecal matter (which was provided by a donor, who was screened for transmissible diseases) by way of oral tablet one week prior to a round of immunotherapy drugs (either pembrolizumab or nivolumab). Out of the 20 participants, 13 (65%) had a positive response to the treatment, with four (20%) of them going into complete remission from their cancer.

This treatment did appear to have side effects. Eight of the patients experienced mild symptoms from the fecal transplant, such as diarrhea, flatulence, and abdominal discomfort. None of the participants developed infections or other serious complications from the fecal transplant. However, there were some more serious side effects from the immunotherapy part of the treatment plan. 17 out of the 20 participants experienced side effects from the immunotherapy treatment, with five study participants having severe side effects that required termination of immunotherapy treatment. These side effects included arthritis, pneumonitis, and nephritis.

Many more studies will have to be conducted before this can be declared a safe and effective treatment for colon cancer, but this initial investigation is certainly promising. Read more about cancer research here.