Probiotic Supplements May Reduce the Effectiveness of Immunotherapy

Do Probiotics Reduce the Effect of Immunotherapy?

Cancer immunotherapy offers a highly effective treatment for cancer types resistant to chemotherapy and radiotherapy. Immunotherapies aim to use mechanisms that activate the immune system against cancer cells, providing longer survival with few adverse effects. Recently, factors that increase or decrease the effectiveness of cancer immunotherapy have been investigated. At the ongoing American Association for Cancer Research (AARC) congress in Atlanta in 2019, probiotic supplement use was observed to reduce the response to immunotherapy by 70 percent.

One of the 10 hallmarks of cancer is learning to evade the immune system. Immune checkpoint inhibitors enable immune cells to attack cancer cells. However, these drugs are effective in 20-30 percent of patients.

Researchers from the United States examined the role of probiotics in cancer immunotherapy. The study included 113 patients with metastatic melanoma (skin cancer). Participants completed questionnaires about diet, medication, and supplement use. Fecal (stool) samples were also collected to analyze intestinal bacterial density. Participants were additionally followed throughout treatment.

According to the Research Results

• Probiotic supplements were observed to reduce the response to immunotherapy by 70 percent.
• It was found that 42 percent of participants took probiotic supplements.
• Probiotics were found to reduce bacterial diversity in the gut.
• High-fiber diets were found to increase the response to immunotherapy 5-fold. These vegetable-rich diets increase the number of healthy bacteria in the gut.

What Does This Study Mean for Us?

• Probiotics were discovered to reduce the effectiveness of immunotherapy.
• The general belief about probiotics is that they improve the health of the intestinal microbiome. This may not apply to patients with cancer.
• Clinical trials addressing this subject are being planned.
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