High-fiber diet linked to immunotherapy response among patients with melanoma
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A high-fiber diet appeared associated with increased PFS among patients with melanoma who started treatment with immune checkpoint inhibitors, according to study results published in Science.
Researchers observed the most pronounced benefit among patients who did not take commercially available probiotic supplements.
“Sufficient dietary fiber intake was associated with improved response to immunotherapy and in preclinical models, dietary fiber manipulation impacted antitumor immunity,” Jennifer McQuade, MD, assistant professor of melanoma medical oncology at The University of Texas MD Anderson Cancer Center, told Healio. “The dietary pattern associated with response to immunotherapy is the same diet recommended by American Cancer Society and American Institute for Cancer Research, which includes a diet rich in fruits and vegetables, whole grains and legumes. This diet is also recommended for secondary cancer prevention and prevention of cardiovascular disease and health in general.”
Rationale
Previous research has shown gut microbes may regulate response to immune checkpoint inhibitors. However, the effect of diet and probiotic supplement use among patients with melanoma receiving treatment with checkpoint inhibitors had not been studied extensively.
“We know that diet is a key determinant of the gut microbiome from studies in healthy populations. In particular, the gut microbes associated with response to immunotherapy are bacteria that help us digest fiber,” McQuade said.
Methodology
McQuade and colleagues conducted a randomized prospective clinical trial to assess how varying fiber intake affects the gut microbiome and immune response among 128 patients with advanced melanoma receiving treatment with immune checkpoint inhibitors.
Researchers examined fecal microbiota profiles, dietary habits and commercially available probiotic supplement use, and performed parallel preclinical studies.
Key findings
Patients who reported a higher consumption of dietary fiber intake from fruits, vegetables, legumes and whole grains experienced significantly longer PFS. Median PFS was not reached among the 37 patients with sufficient fiber intake, compared with median PFS of 13 months among the 91 patients with insufficient fiber intake.
Researchers also reported that every 5-g increase in daily fiber intake correlated with an approximately 30% lower risk for cancer progression or death (HR = 0.71; 95% CI, 0.52-0.98).
Moreover, 82% of patients who reported both sufficient fiber intake and no probiotic use responded to immunotherapy, compared with only 59% of patients who reported either insufficient fiber intake or probiotic use. The preclinical models produced similar results.
Probiotic supplement use alone did not appear associated with a significant difference in PFS or response to immunotherapy, according to the researchers.
Implications
Based on these findings, oncologists should recommend a plant-forward, fiber-rich diet to patients, with the caveat that there are no data in patients proving that a change in diet at start of immunotherapy will impact outcomes, McQuade said.
“This is our next step in research. We plan to test the hypothesis that diet intervention will favorably modulate the gut microbiome and enhance immunity,” she said. “We have just completed accrual for our phase 1 feasibility study of a controlled diet intervention in which all food is provided to a cohort of survivors of melanoma over the duration of the study. Both the microbiome and immune response will be longitudinally assessed. We are now enrolling on our randomized phase 2 study of two different healthy diet interventions with varying fiber content in patients with melanoma receiving immunotherapy.”
For more information:
Jennifer McQuade, MD, can be reached at The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030.
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