Fecal transplants could be a secret weapon for some patients battling skin cancer

• A new study used fecal transplants from a healthy donor on 20 skin cancer patients.
• 65% of patients responded to the combination of a transplant and immunotherapy.

Researchers may have found an unlikely tool to help treat skin cancer: Fecal transplants.

In a new study published in Nature Medicine on July 6, researchers transplanted the stool from one healthy donor into 20 patients with advanced melanoma who were about to undergo immunotherapy. The idea was to transfer the donor's microbiome into the patients to promote the growth of healthy bacteria in their guts and improve their cancer treatment results.

While the study's primary goal was to see if this treatment is safe to try on patients, the findings were promising: 65% of patients responded to the combined treatment of fecal transplants and immunotherapy.

"These exciting results add to a rapidly growing list of publications suggesting that targeting the microbiome may provide a major advance in the use of immunotherapy for our patients with cancer," said Dr. Wilson H. Miller Jr., one of the researchers and a professor in the Departments of Medicine and Oncology at McGill University, in a press release from Lawson Health Research Institute where the research was conducted.

Improved gut health can make immunotherapy more effective

Immunotherapy is a relatively new innovation and has grown in popularity as a skin cancer treatment. It works by boosting the body's immune system and helping T-cells identify and attack cancer cells. The specific immunotherapies tested in this study are called immune checkpoint inhibitors, or PD-1 inhibitors.

PD-1 inhibitors can be a breakthrough treatment for some people with cancer, but for other people it has mixed or no results — about 40% of melanoma patients don't respond to the treatment.

To improve this resistance to treatment, researchers in the study took a healthy donor's fecal matter, screened and prepared it in a lab, and then gave it to each patient in the form of 40 oral capsules a week before they started immunotherapy.

Gut health and the immune system are closely connected. Dr. Bertrand Routy, oncologist and director of the Centre hospitalier de l'Université de Montréal's Microbiome Center, told CTV News that fecal transplants could "eliminate certain bacteria that are associated with resistance to immunotherapy" as well as increase the bacteria that aid treatment.

There's still some mystery as to why fecal transplants work

While fecal transplants have been used to treat everything from C-section babies to auto-brewery syndrome, researchers are still trying to maximize their effectiveness.

Routy told CTV News that "we're beginning to understand which bacteria are associated with resistance and which bacteria are associated with the right response." He also said that the fecal compatibility between a specific donor and a patient can also play a role in the treatment's success.

More research is still needed

Because phase I of the experiment was deemed safe, researchers are now moving on to phase II, where they will test the effectiveness of fecal transplants in a larger group of cancer patients, according to the press release.

It's still too early to know if fecal transplants will be a good treatment in the long run. A 2019 study found that 45-65% of melanoma patients respond to PD-1 inhibitor treatment without fecal transplants anyway.

Lawson researchers also plan to study the use of fecal transplants in other cancers, such as renal cell carcinoma, pancreatic cancer, and lung cancer, the press release said, and they're also exploring how this method can impact treatments for HIV and rheumatoid arthritis.