Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response

Merkelcell.org Summary

We are what we eat, and to investigate this, researchers studied the impact of dietary habits on the gut microbiome and treatment success of 128 melanoma patients. The gut microbiome is the community of tiny invisible organisms in our intestines and might affect how well immunotherapy, a treatment that helps the immune system fight cancer, works.

The study found that among 123 patients, those who ate at least 20 grams of fiber (e.g. 100 grams uncooked whole grains. 1 cup of cooked beans. 2-3 servings of fruits) daily had an 82% response rate to immunotherapy, compared to a 59% response rate for people who ate less than 20 grams. They also observed that for every extra 5 grams of fiber eaten daily, the risk of the cancer getting worse dropped by 30%. Surprisingly, taking over-the-counter probiotic supplements was linked to worse survival and a poorer response to immunotherapy in this particular study. Probiotics are live bacteria and yeasts that help maintain a healthy gut microbiome and can be taken as a supplement or found in foods such as yogurt, sauerkraut, miso, or other fermented foods. Studies in mice suggest that taking over-the-counter probiotics could lead to a poorer immunotherapy response because probiotics lower the number of cancer-killing T-cells found in tumors, which are immune cells that help fight cancer.

Overall, in this study, melanoma patients who ate high-fiber diets (more than 20 grams daily) and avoided probiotic supplements had the best responses to immunotherapy and lived the longest. Although more research is needed, this study highlights the importance of diet in influencing gut health and the immune system, and how simple dietary changes could potentially impact how effective immunotherapy is. Patients on immunotherapy could consider eating more fiber and lifestyle modifications. However, since individual needs can vary, working with a dietitian for personalized advice is recommended if possible.

Abstract

Gut bacteria modulate the response to immune checkpoint blockade (ICB) treatment in cancer, but the effect of diet and supplements on this interaction is not well studied. We assessed fecal microbiota profiles, dietary habits, and commercially available probiotic supplement use in melanoma patients and performed parallel preclinical studies. Higher dietary fiber was associated with significantly improved progression-free survival in 128 patients on ICB, with the most pronounced benefit observed in patients with sufficient dietary fiber intake and no probiotic use. Findings were recapitulated in preclinical models, which demonstrated impaired treatment response to anti–programmed cell death 1 (anti–PD-1)–based therapy in mice receiving a low-fiber diet or probiotics, with a lower frequency of interferon-γ–positive cytotoxic T cells in the tumor microenvironment. Together, these data have clinical implications for patients receiving ICB for cancer.