TORONTO — Fecal transplants — the transfer of stools from a healthy donor into the gastrointestinal tract of another — can help patients respond better to cancer treatments according to a new, though small, study published Thursday in Science.
A team of researchers transplanted fecal samples via colonoscopy to patients with advanced melanoma, a form of skin cancer, who had previously not responded to “all available therapies”. They were then given the anti-PD-1 drug pembrolizumab, a type of cancer treatment. The samples, which were screened for infectious disease, were originally taken from patients who had responded extremely well to that type of cancer treatment.
The results found that six of the 15 patients with advanced melanoma who received the fecal microbiota transplants (FMT) were able to stabilize their cancer or get their tumours reduced for more than a year, according to the proof-of-principle, phase II clinical study by researchers with the UPMC Hillman Cancer Center and the National Cancer Institute (NCI).
“The likelihood that the patients treated in this trial would spontaneously respond to a second administration of anti-PD-1 immunotherapy is very low,” a Dr. Hassane Zarour, the study’s co-senior author and cancer immunologist at UPMC Hillman, said in a statement. “So, any positive response should be attributable to the administration of fecal transplant.”
Fecal transplants are a good way to help test trillions of microbes at once, so NCI researchers analyzed the microbiome samples to better understand why the transplant appeared to help boost a patient’s response to the treatment.
“We know the composition of the intestinal microbiome — gut bacteria — can change the likelihood of responding to immunotherapy. But what are ‘good’ bacteria? There are about 100 trillion gut bacteria, and 200 times more bacterial genes in an individual’s microbiome than in all of their cells put together,” said Dr. Diwakar Davar, the co-lead author of the study and a medical oncologist at UPMC Hilman.
The analysis of samples taken from the patients who received the transplants found that there were immunological changes in the blood and at the location of the cancer. This suggested that there was an increase in the number of immune cells activated for those who respond to treatment and an increase in immunosuppression, where the body’s ability to fight infections and diseases is suppressed, in those who did not respond to treatment. These changes have been linked to changes in the gut microbiome, which was likely a result of the fecal transplant, according to the scientists.
The study was conducted over a 12-week period, and up to 24-weeks in patients who responded to treatment.
Going forward, Zarour and Davar, who also both teach at the University of Pittsburgh School of Medicine, hope to run a larger study and also explore whether FMT can also help treat other types of cancers. The eventual goal, years down the road, is to develop a cocktail of the best microbes that can be given to cancer patients in a pill form instead of through FMT.
Fecal transplantation has been done in other areas of medicine, notably as a treatment for recurrent inflammation of the colon. Antibiotics can kill off a lot of the good bacteria in the cut, and the transplant can help restore them.
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