The risk of developing colitis - inflammation in the lining of the colon - as a side effect of cancer immunotherapy may be predicted by a fecal test, suggests a study in Nature Communications. Immunotherapy involves enlisting a patient’s own immune cells to fight tumours; however, this immune response may also be directed towards the patient’s healthy tissues, causing autoimmune diseases such as colitis. Knowing in advance which patients are at risk would allow this side effect to be minimized.
Colitis has previously been correlated to changes in microbial composition, but establishing causative links has been difficult in humans. Although clinical trials are needed, this study identifies possible biomarkers that may allow the identification of patients susceptible to immunotherapy-induced colitis.
Eric Pamer and colleagues measure the composition of microbes and metabolites in fecal samples from 34 patients suffering from melanoma. They analyse the samples prior to immune therapy, when the patients did not suffer from intestinal inflammation. They show that one third of the patients developed colitis within weeks following the treatment, and that those who developed colitis lacked a type of intestinal bacteria called Bacteroidetes, and specific metabolites made by gut bacteria, prior to immunotherapy.
This study suggests that Bacteroidetes and specific microbial metabolites may be potentially used for protection of these patients. These results could enable interventions to reduce the risk of inflammatory complications following cancer immunotherapy.