Gut Health May Impact Side Effects Risk From Certain Melanoma Treatment

Certain gut microbes, or bacteria in the gut, may influence side effects experienced by patients with melanoma who are treated with combined checkpoint inhibitors, according to a study published in Nature Medicine.

“We know that within our bodies, there are hundreds of trillions of microbes, bacteria and viruses … that can actually profoundly impact how our body functions,” said senior study author Dr. Jennifer Wargo, professor of genomic medicine and surgical oncology at The University of Texas MD Anderson Cancer Center, in an interview with CURE®. “And we know from recent work that the microbes or the bacteria and viruses … that inhabit our gut, or gastrointestinal tract, can actually influence how our immune system functions and can actually influence responses to cancer treatment.”

Wargo hypothesized that if health care teams are able to screen gut bacteria through fecal samples, they may be able to increase the effectiveness of a cancer treatment, as well as better understand the influence that gut bacteria has on common side effects that occur from combined checkpoint inhibitors in patients with melanoma.

“When you treat with these combinations, sometimes patients get pretty severe (side effects) This includes colitis, … other forms of toxicity, thyroiditis,” Wargo said. “They can have all kinds of inflammation that occurs in the setting of this treatment, and so we wanted to better understand how the bugs in the gut might influence toxicity to cancer treatment, particularly with this combined cancer treatment.”

Researchers examined the biomarkers of response and toxicity to immune checkpoint inhibitors in 77 patients with advanced melanoma. During the study, the patients provided tumor, blood and fecal samples. Nearly half of the patients experienced severe or life-threatening side effects with the treatment.

“We actually saw very striking signals with regard to toxicity where we saw (that) specific bacterial taxonomy (the biology of the bacteria) were associated with toxicity to the cancer treatment,” she explained.

Wargo said that, although preliminary, the data may help health care teamstarget the specific bacteria and deplete the bugs, making the patient less likely to develop severe side effects. Screening for the bacteria prior to deciding upon a treatment regimen may also help teams to better decide which treatment type will work best.

“These gut microbes do have a profound impact on our physiology and on cancer treatment. We're learning more and more about that every day, but it's not the only piece of the puzzle,” Wargo said.

Other “puzzle pieces” to look into include lifestyle exposures such as diet, anxiety or obesity that could also affect the gut environment.

“I think it (is in the) early days still. We don't have all the answers,” she explained. “Certainly, we don't know what the optimal microbiome is. We have some clues and some hints with regard to how we could potentially promote response and also now reduce toxicity. I think it's a start.”

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