Ask the doctors: Researchers studying how gut microbiome affects cancer treatment

Dear Doctor: I read that microbes can affect how our body deals with immunotherapy. A friend of mine is about to start immunotherapy for lung cancer. Is there anything she can do to increase the chances that her gut will help her body beat this cancer?

Dear Reader: Your question sends us into the brave new world of precision medicine, which is rapidly transforming how we approach cancer treatment. Unlike chemotherapy, which targets all of the fast-dividing cells within the body no matter their origin, or radiation, which kills cancer cells by damaging the DNA in all of the cells in its path whether they are healthy or cancer cells, immunotherapy approaches cancer quite precisely, and at the cellular level. The point isn’t so much to destroy cancer cells as to disrupt them.

For instance (and very broadly – it’s far more complex than our space here allows), researchers have designed antibodies that disable cancer cells by targeting specific sites within those cells. They have also created chemo- and radiolabeled antibodies, which deliver microdoses of powerful anti-cancer drugs and radiation to cancer at the cellular level. In an approach known as “adoptive T cell transfer,” a patient’s own immune cells are collected, modified to enhance cancer-fighting properties, and then re-infused.

Now, new research suggests that this targeted approach can be bolstered by beefing up a patient’s own gut microbiome, which is the vast and varied collection of microbial communities that live within each of us. This is important because, although immunotherapy is brilliant in theory, in practice the results thus far have been mixed.

That’s because the immune system is so alert to intruders of any kind that the presence of the immunotherapy drugs themselves can set it off. Side effects of immunotherapy can include rashes, fever, headache, weakness, elevated liver enzymes, low blood cell counts, breathing issues, diarrhea and vomiting. In some cases, adverse reactions to immunotherapy can be severe enough to be life-threatening. In exploring avenues to help a patient’s body tolerate immunotherapy, researchers looked to the gut microbiome.

According to a pair of studies featured in the journal Science, the patients who responded best to treatment with a certain class of immunotherapy drugs were those with the more diverse and robust microbiomes.

One study, done by researchers in Texas, focused on patients with melanoma. The other, conducted in France, included patients who had undergone a course of antibiotics to deal with lung, bladder and kidney cancer. The French researchers found that patients who had undergone a course of antibiotics to deal with problems like a urinary tract infection had the poorest response to immunotherapy. The Texas researchers are now planning to check their results with a clinical trial. The research has reportedly caught the interest of several biotech companies, which are also doing clinical research into the matter.

Meanwhile, your friend can take steps to improve her own microbiome. These include adding fermented foods and beverages to her diet, eating high-fiber fresh fruits and vegetables to provide plenty of nutrients for her microbial community, and steering clear of artificial sweeteners and processed foods. Finally, we believe it would be wise for her to enlist her health care team in this endeavor.