Researchers Find Correlation Between Gut Microbiome and Immunotherapy Response in Melanoma

Bacteria in the gut microbiome is associated with disease progression or delay in patients with metastatic melanoma who were treated with immunotherapy, according to a study presented at the 2017 American Society of Clinical Oncology Annual Meeting.

Researchers from The University of Texas MD Anderson Cancer Center studied fecal samples from 105 patients with immune checkpoint blockers and found that a greater diversity of bacteria in the gut microbiome was associated with a higher response rate to treatment and a longer progression-free survival.

“The microbiome appears to shape a patient’s response to cancer immunotherapy, which opens potential pathways to use it to assess a patient’s fitness for immunotherapy and to manipulate it to improve treatment,” study leader Jennifer Wargo, MD, associate professor of Surgical Oncology at MD Anderson, said in a statement.

The researchers conducted an analysis of the presence of 16S ribosomal RNA to identify bacteria and determine microbiome composition from fecal samples.

Patients with metastatic melanoma were treated with a PD-1 inhibitor and at the median time to follow-up of 242 days, more than half of patients with high microbiome diversity had not had disease progression. Meanwhile, patients with a lower microbiome diversity had a median progression-free survival (PFS) of just 188 days.

In addition to bacteria diversity, specific types of bacteria had an impact. More than half of patients with an abundance of F. prausnitzii had not reached median PFS.

Despite the findings, Wargo cautioned against people self-medicating with probiotics and other methods. There still needs to be a better understanding of the relationship between the microbiome and cancer treatment.

Wargo’s team is collaborating with the Parker Institute for Cancer Immunotherapy to develop the first immunotherapy-microbiome trial to potentially launch later this year. They are also conducting lab and mouse model research on the connection between bacteria and the immune system.