What’s in Your Gut? Bacteria Might Impact Response to Cancer Therapy

Nov. 2, 2017

A melanoma patient’s gut bacteria—“favorable” or “unfavorable”—influences whether that person responds to immunotherapy treatment, according to a new study published in Science.

A more diverse gut microbiome, filled with plenty of good bacteria, was associated with better outcomes among 112 patients with metastatic melanoma who were observed for six months while taking anti-PD1 therapy. (Anti-PD1 drugs became more widely known after former President Jimmy Carter began using them to control his metastatic skin cancer. The drug works by boosting the body’s natural immune fighters against cancer cells.)

head and shoulders of Peter Prieto, MDThe study’s results are exciting because scientists were able to correlate, to a specific microbiota, a patient’s immune system’s ability to combat cancer, said co-author Peter Prieto, M.D. M.P.H., assistant professor of Surgery at the University of Rochester Medical Center and Wilmot Cancer Institute.

“And just as importantly, our results will lead to new strategies, such testing potential probiotics in clinical trials to boost the response of standard treatments for melanoma,” Prieto said.

Prieto participated in this research project while at the MD Anderson Cancer Center in Texas before he joined the faculty at URMC, where he’s continuing his microbiome investigation.

For the current study, researchers collected oral and fecal samples from the 112 patients with metastatic melanoma, and also collected blood samples and assessed tumor biopsies for gene alterations. Then, scientists performed gene sequencing on the bacteria samples and simultaneously observed the patients for six months to see how they responded to anti-PD1 immunotherapy treatment. Patients were classified as “responders” if their tumors disappeared or stabilized. Individuals with a more diverse gut microbiome—including an abundance of “good” bacteria such as Rumunococcaceae/Faecalibacterium—responded better to the cancer treatment and had more prolonged responses. Learn more in the full study.

The ultimate goal, Prieto said, is to identify a “microbiome signature,” like a living biomarker in the form of healthy bacteria. In the meantime, consumers, cancer patients, and the medical community should be concerned about the overuse of antibiotics, which contributes to unhealthy gut flora and limits immune function, he said.

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