Some patients with melanoma, lung and head and neck cancers are responding strongly to a new class of immunotherapy drugs called checkpoint inhibitors, research shows. But other patients aren’t responding at all. The effort to explain the disparity between cancer patients who benefit from the drugs and those who don’t has led scientists to an unexpected place: the gut—specifically, the microbes taking up residence there.
Writing in the journal Science, independent groups of cancer researchers who conducted two separate mouse studies found that some cancer treatments may be more effective if certain key microbes are present in the rodents’ digestive systems. Microbes in the Bifidobacterium family, B. fragilis and B. thetaiotamicron, stimulated the animals’ immune anti-cancer response, scientists found. The studies have also prompted interest from multiple pharmaceutical companies that want to see further studies in humans, according to a recent report from Bloomberg News. "It’s one of the most interesting developments we’ve seen in science over the last several years," Daniel Chen, head of cancer immunotherapy research at Roche’s Genentech division, told Bloomberg.
Naturopathic clinicians have long been recommending probiotics, including those that include Bifidobacterium species, based on multiple studies that show health benefits for digestion, anxiety, inflammation, immunity and other conditions, says Daniel Kellman, Clinical Director of Naturopathic Medicine at our hospital near Atlanta. The interplay between our cells and the trillions of bacteria that inhabit our bodies is a rapidly growing area of study.
“Beneficial gut bacteria produce anti-inflammatory factors, pain-relieving compounds, antioxidants and even vitamins, ”Kellman says. “Keeping the good bugs present and healthy really helps in keeping us healthy.”
Cancer patients often take strong antibiotics during their treatment journey, and that may change the composition of their gut microbiome, Kellman notes. That may make them especially vulnerable to gastrointestinal challenges. Harmful bacteria like C. difficile sometimes proliferate after antibiotic use, causing diarrhea. Probiotics may help protect against such complications. Vitamin D and other nutritional supplements may also help modulate the immune system, depending on a patient’s individual needs, Kellman says.
The so-called “checkpoint inhibitor” immunotherapy drugs, which include ipilimumab, nivolumab and pembrolizumab, work by unlocking the brakes that prevent people’s immune systems from attacking cancer. Kellman urges patients to be careful about taking supplements with immune-boosting properties during immunotherapy treatments. Patients on average should receive two immunotherapy infusions before introducing supplements, to gauge whether additional support is needed. “We need to be careful about there being overreactions in the immune system,” Kellman says. Studies have shown immunotherapy drugs may have the potential to provoke autoimmune reactions like enterocolitis in some patients.
The studies published in Science were conducted in mice, not humans, and further study is needed, Kellman emphasized. But the hope for improving cancer patients’ response to immunotherapy is promising. “Humans really are a superorganism,” he says. “So maintaining the balance of the human gut flora is really important.”
Learn more about how naturopathic medicine may help during cancer treatment.