Melanoma Coverage from Every Angle

AACR 2019: Impact of Probiotics and Fiber on Gut Microbiome and Immunotherapy Response

By: Anna Nowogrodzki
Posted: Thursday, April 4, 2019

Patients with melanoma who said they ate a high-fiber diet were more likely to respond to anti–PD-1 immunotherapy than those who said they ate a low-fiber diet, according to the results of a new study that relied on self-reported diet and supplement use. Use of probiotics or antibiotics was correlated with lower gut microbiome diversity. The research was presented at the 2019 American Association for Cancer Research (AACR) Annual Meeting by senior author Jennifer Wargo, MD, MMSc, of Parker Institute for Cancer Immunotherapy, San Francisco, and colleagues.

“Based on these preliminary results, we need to reconsider use of over-the-counter probiotics in patients with cancer, at least until we have more data supporting their potential safety and efficacy,” said Dr. Wargo in an AACR press release.

Before treatment, the researchers sequenced fecal samples of 146 patients with melanoma to characterize their gut microbiomes. Of these patients, 113 received systemic treatment and a questionnaire about their diet and use of probiotics and antibiotics. A subset of 46 patients received anti–PD-1 immunotherapy.

Patients with a complete or partial response to any type of therapy had higher gut microbiome diversity than those with stable or progressing disease. Those who said they used probiotics (42%) or antibiotics (29%) had lower gut microbiome diversity on average. Patients who said they ate a high-fiber diet were about five times more likely to respond to anti–PD-1 immunotherapy than those who ate a low-fiber diet.

In previous research, coauthor Christine N. Spencer, PhD, of The University of Texas MD Anderson, Houston, and colleagues reported that patients with melanoma who had a gut microbiome enriched in bacteria of the Ruminococcaceae family appeared to be more likely to respond to anti–PD-1 treatment. Eating more whole grains, fruits, vegetables, and fiber seemed to be correlated with more of these bacteria, whereas eating more added sugar and processed meat seemed to be linked to fewer of them.

Disclosure: The study authors’ disclosure information may be found at

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