Fecal transplants could help patients on cancer immunotherapy drugs
What if response to immunotherapy depends on the microbes inside the intestine? An unusual treatment involving stool transplantation from one patient to another could help those who do not respond to immunotherapy.
Some people do not benefit from immunotherapy. One might think it was due to either cancer or immune cells, but several studies show that gut microbes are just as important. However, as only some people respond to treatment, some bacteria must be “better” than others. Could we transplant those microbes into a non-responder patient?
What is in your faeces?
That is where faeces come in. Not the classic topic of conversation, faeces can cause disgusted or embarassing reactions. However, the restoration of the bacterial flora through faecal transplantation is consolidating as a strategy for the treatment of infections and chronic pathologies. Faeces are composed of 74% water, but the solid part contains bacterial mass in a significant percentage, which varies between 25% and 54%. Moreover, the composition of bacteria in the faeces recapitulates that of the intestine.
An unusual transplant
Numerous studies suggest that patients could benefit from that "particular" transplant. In fact, this is currently recommended against Clostridium difficile infections, which cause inflammation of colon and intestine. Now it is time to investigate the potential of faecal transplantation to treat other gastrointestinal disorders (constipation, allergic colitis) as well as metabolic or neurological diseases and even cancer.
Gut microbes for cancer immunotherapy
Gut microbes could also help patients on immunotherapic drugs. People who respond to treatment had a higher microbial diversity with respect to non responders. We do not know yet which species do most of the job or what is their mechanism of action. However, a patient who has benefits from immunotherapy, should probably also thank his bacteria.
Several groups are working on this idea that we can collect stool samples from patients whose tumors vanished upon treatment and transfer them into patients with the same kind of cancer, but resistant to drugs. The first experiments led by Gal Markel at Sheba Medical Center in Ramat Gan, Israel and by Giorgio Trinchieri of the National Cancer Institute in Bethesda, Maryland, have provided promising results. Therefore it is really worth it to overcome the initial feeling of disgust and open the doors to a new treatment, which could improve the efficacy of immunotherapy on patients.
Erika Salvatori
Reference:
Fecal Microbiota Transplantation (FMT) in Metastatic Melanoma Patients Who Failed Immunotherapy https://clinicaltrials.gov/ct2/show/NCT03353402
Bianchieri, P. Et al. (2018). Could Fecal Transplantation Become Part of PD-1-Based Immunotherapy, Due to Effects of the Intestinal Microbiome? Gastroenterology https://doi.org/10.1053/j.gastro.2018.03.060
