Low Microbiota Diversity Prior to Bone Marrow Transplant Linked to Higher Risk for Complications

Intestinal microbiota diversity is critical for keeping harmful bacteria from dominating gut which can results in severe microbiota injury and treatment complications in patients with cancer.

In a new study, presented today, December 3, in an oral abstract session at the 60th Annual American Society of Hematology Annual Meeting in San Diego, California, investigators determined that individuals who had lower microbiota diversity in their intestine prior to a bone marrow transplant had a higher risk for post-transplant complications such as graft-versus-host disease or death.

“Patients who went into the BMT process with a gut flora that was already disrupted had a higher risk of death after the transplant,” Marcel van den Brink, MD, PhD, chief of Memorial Sloan Kettering’s (MSK) Division of Hematologic Malignancies and senior author of the study, said in a recent statement said. “The thing that we keep coming back to is that preserving the commensal flora in the microbiome is good for transplant patients.”

In a multicenter analysis, international investigators led by a team at MSK Cancer Center hypothesized that the microbiota configuration prior to transplant could be an important determinant of post-transplant complications.

To investigate their hypothesis, the investigators examined 1922 stool samples from 991 individuals undergoing allogenic bone marrow transplants. The participants in the study were all adults undergoing transplants at MSK, Duke University School of Medicine in Durham, North Carolina, Hokkaido University in Sapporo, Japan, or University Hospital Regensburg in Regensburg, Germany.

After analyzing the samples, the investigators found that on average, prior to transplants, the participants had a gut microbiota that was 1.7 to 2.5-fold lower in diversity compared with healthy volunteers. Additionally, the strains of bacteria that were present and more common in the transplant patients were different than those of the healthy volunteers.

Furthermore, the participants with the lowest microbial diversity showed lower overall survival and a higher risk for graft-versus-host disease.

“Before someone has a BMT to treat their cancer, we do a lot of screening tests to make sure they are otherwise healthy. We look at things like their heart, lung, and kidney functions,” Dr. van den Brink added. “This study suggests that we should also screen the microbiota. If we find out that it’s in bad shape, we could do something to repair it.”

The authors noted that the study did not examine how gut microbes might influence the process of the transplant or lead to complications. They are studying the relationship between microbes and the activation of T cells in transplants, but more research is needed to understand if the relationship can lead to a decrease in protective bacteria or increased harmful species.

However, the team indicates that this particular study further supports evidence that there is a connection between microbiota and patient outcomes that starts prior to the transplantation process. This information provides the opportunity for clinicians to work to repair the microbiota prior to the transplant. Possible interventions to improve the microbiota health could include avoidance of certain antibiotics, changes in diet or calorie intake, or fecal transplants of healthy gut microbes.