The sooner doctors can identify an effective treatment, the better a cancer patient's chance of beating their disease — but finding that treatment can be a painful, time-consuming, and expensive process.
Cancer treatments fall into at least eight categories, each containing multiple options for drugs or therapies, and two patients with the exact same type of cancer can require completely different treatment regimens.
Now, researchers appear to have found a way to make one type of cancer treatment work for more people: fecal transplants.
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The 411 on Fecal Transplants
The human gastrointestinal tract, or gut, contains trillions of viruses, bacteria, and other germs, known collectively as the "gut microbiome."
Many of these microbes are helpful — they combat infections and help our bodies break down food — but others are harmful.
That imbalance has been linked to a variety of diseases, and not just ones centered on the gut — rheumatoid arthritis, muscular dystrophy, and multiple sclerosis are just a few examples.
That's where fecal transplants come into play.
These are exactly what they sound like: a feces sample is taken from a healthy person and transplanted into the patient. This can improve the balance of bacteria in the recipient's gut, potentially helping them overcome a health issue.
The procedure was initially used to treat a bacterial infection called C. difficile, but research suggests it may help treat a variety of other conditions, including IBS, diabetes, autism, and age-related cognitive decline.
A Promising Skin Cancer Treatment
For this new study, researchers from the National Cancer Institute and the University of Pittsburgh set out to see whether fecal transplants could help people with advanced melanoma.
Melanoma is a rare but serious form of skin cancer, and once it reaches the advanced stage, that means the cancer has spread to other parts of a patient's body.
Advanced melanoma is hard to treat, and about 75% of people with it die within five years of being diagnosed. However, a type of immunotherapy drug called an "immune checkpoint inhibitor" has been shown to help about 40% of patients with the disease.
"Altering the composition of the gut microbiome can improve the response to immunotherapy."
Immune checkpoints are a natural part of our immune system, and their role is to prevent an immune response so strong that it kills healthy cells. Immune checkpoint inhibitors essentially release the brake, letting the immune system loose to target and kill tumor cells.
Most melanoma patients still don't respond to these drugs, and the researchers had reason to suspect that their microbiomes might have something to do with that. Past research had shown links between the microbiome and the immune system, and microbial transplants in unresponsive mice had been shown to improve immunotherapy.
To test whether the same would be true of human cancer patients, the researchers obtained fecal samples from patients who did respond to the drugs and transplanted them into 15 patients who didn't respond initially.
Then they tried the immune checkpoint inhibitors again. This time, six of the 15 patients responded to the drug — either their tumors shrank or they experienced long-term stabilization of their disease.
More Melanoma Trials
The researchers say that, normally, the odds that a second round of immunotherapy would work on an initially unresponsive patient is "very low" — much lower than the one-third response rate seen in this study. This suggests that the fecal transplants really were responsible for the positive outcomes in the trial.
"Our study is one of the first to demonstrate in patients that altering the composition of the gut microbiome can improve the response to immunotherapy," researcher Giorgio Trinchieri said in a press release.
"The data provide proof of concept that the gut microbiome can be a therapeutic target in cancer," he added.
After the fecal transplants, six of the 15 patients responded to the drugs.
They're now calling for larger trials to check their study's results and potentially identify biomarkers indicating a patient's likely response to immune checkpoint inhibitors.
Those biomarkers could help doctors determine which patients are naturally going to be receptive to the immunotherapy drugs and which might benefit from fecal transplants first — this could cut down on the critical time it takes to arrive at an effective cancer treatment.
If future studies can identify exactly which microbes are helping the response to the drugs, fecal transplants might not even be necessary — doctors could just implant those organisms into patients, eliminating any risk of introducing something unwanted.
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