High-fiber diet tied to better immunotherapy response and progression-free survival in melanoma

Reuters Health - 03/01/2022 - Patients with melanoma who ate more fiber-rich foods when starting immunotherapy responded better to therapy and had improved progression-free survival compared to those who did not get enough dietary fiber, researchers say.

Further, taking commercial probiotic supplements did not help treatment outcomes.

"Though we were not surprised (by) the findings that increased dietary fiber intake was associated with better outcomes, the strength and magnitude of this association was somewhat surprising to us," Dr. Jennifer Wargo of the University of Texas MD Anderson Cancer Center in Houston told Reuters Health by email. "In addition, the low proportion of patients reporting 'sufficient' dietary fiber (29%) was eye-opening."

"The findings regarding use of commercially available probiotics were quite surprising (31% of our patients)," she said. "Importantly, when we considered dietary fiber and probiotic use together, we found that patients with sufficient dietary fiber intake who reported use of commercially available probiotics had worse outcomes than those who did not report (probiotics) use."

Coauthor Dr. Carrie Daniel-MacDougall, also of MD Anderson, noted in the same email, "Gut health and host health both need to be considered. A balanced diet with fiber-rich foods is one way to safely address both at the same time, and one key reason why we feel it holds strong promise. These are the same healthy foods encouraged across national dietary recommendations and by organizations such as the American Institute for Cancer Research, which define diet and lifestyle recommendations across the cancer continuum."

As reported in Science, the team analyzed the fecal microbiota of 438 melanoma patients, 293 of whom had an evaluable response to treatment during follow-up. Most (87%) received immune checkpoint blockade (ICB), most commonly, PD-1 inhibitors.

One hundred and fifty-eight patients completed a survey of antibiotics and probiotics use, and of these, 128 also completed a dietary questionnaire when they began therapy.

The 37 patients with sufficient fiber intake had improved progression-free survival (median not reached) compared to the 91 patients with insufficient fiber intake (median, 13 months). After adjustment for clinical factors, every 5-gram increase of daily fiber intake was associated with a 30% lower risk of cancer progression or death.

Response to IBD was seen in 82% of patients who reported both sufficient fiber intake and no probiotic use, compared to 59% of those who reported either probiotic use or insufficient fiber intake.

Probiotic use alone was not associated with a significant difference in progression-free survival or odds of response to immunotherapy.

Findings of multiple experiments in mouse models of melanoma recapitulated patient findings. Probiotic use was associated with impaired ICB response, larger tumors, lower gut microbiome diversity and fewer cytotoxic T cells in the tumor microenvironment.

By contrast, in animals treated with PD-1 inhibitors, a high-fiber diet was associated with slower tumor growth and a significantly higher frequency of CD4+ T cells.

Dr. Daniel-MacDougall noted, "Cancer patients may have other concurrent conditions or medications that require special guidance and discussion with their care team. Following a high-fiber diet should also be done in the context of an adequate balance of protein and other important nutrients for the immune system/recovery, such as B12 and iron."

Dena Champion, a registered dietitian and nutritionist at The Ohio State University Wexner Medical Center in Columbus raised several points about the study in an email to Reuters Health.

"The patients were taking a variety of commercially available probiotics, which makes the findings a bit more difficult to interpret," she said. "Were patients that were taking probiotics taking any other supplements? Often times a patient is taking multiple supplements, not just one. It would be interesting to control for this."

"Patients who consumed more whole grains, fruits, and vegetables met the study's guidelines for sufficient fiber and had the best outcomes," she said. "The question is why? Is it the changes in gut microbiome? Is it the phytochemicals or antioxidants inherent in a plant-based diet?"

"I would love to see a study looking at targeted probiotics as opposed to undirected use of commercially available probiotics," she added. "It is possible that there are specific species of probiotics that could be helpful and some that could do harm."

Following a high-fiber diet "is not always feasible in real life," she noted. "If a patient is feeling very poorly, sometimes just eating something is the best they can do, and that is okay. If a patient is mentally struggling, eating a healthy diet can feel too difficult. This is especially true if they don't have a supportive caregiver to help."

"It would be interesting to look at the feasibility of consuming a high fiber diet when undergoing treatment," Champion concluded.

SOURCE: https://bit.ly/3pOgf6h Science, online December 23, 2022.

By Marilynn Larkin



Posted on 3 January 20221 August 2024