Immunotherapy is one avenue of cancer treatment that is working for many patients, but not for others. Medical Oncology specialists still do not know why.
Study of the microbiome as an anticancer response
Researchers collected oral and gut (fecal) microbiome samples from 233 patients with advanced melanoma at the start of their therapy. Among these patients, 93 received anti-PD-1 treatment. The diversity and composition of the oral and gut microbiome were assessed using a molecular technique called 16S rRNA sequencing, which identifies different bacteria according to their genetic markers. The researchers also analyzed the composition and density of various immune cells in patient tumor samples.
Results of the study
In this study they found a link between gut microbes, or the microbiome, and response to immunotherapy. They observed that the ability of patients with advanced melanoma to respond to certain immunotherapy (anti PD-1) depended on the presence of a microbiome and specific bacterial species. This research is still recent, but if validated in larger examples could have significant implications for cancer prognosis and treatment. Specialists need to better understand how the microbiome may influence immune responses, as well as adjust that microbiome so that more patients can benefit from immunotherapy.
Next steps
This research team aims to better understand the biological mechanisms through which the gut microbiome enhances the immune, systemic and antitumor response. The authors are also designing clinical trials to corroborate the hypothesis that modulation of the gut microbiome can improve responses to immunotherapy. In collaboration with the Parker Institute for Cancer Immunotherapy, the first such trial is expected to begin later this year. At the same time, studies are planned that will explore how best to adjust the composition of the microbiome. In addition to fecal transplantation, other strategies could involve the use of antibiotics to deplete certain bacteria or pre- or probiotic supplements to enhance some bacteria in the gut.