The effect of probiotics and diet on response to immunotherapy has been delved into in a new paper from the Parker Institute for Cancer Immunotherapy and MD Anderson Cancer Center. The controversial study claims the digestive health supplement could reduce the response of patients to this cancer treatment, owing to the way it impacts the gut microbiome. Specifically, the paper discusses a 70% decreased chance of responding to a certain type of immunotherapy when consuming probiotics.
Diet has long been a way that people have attempted to complement conventional cancer treatment, hoping to amplify any results. Though there is little scientific support for these as yet, Cancer research UK talks about the macrobiotic diet and Gerson therapy that both change food intake, as popular among patients. Due to popularity, it stands to reason that diet should be formally investigated as a potential
Researchers from the Parker Institute for Cancer Immunotherapy (PICI) and The University of Texas MD Anderson Cancer Center conducted a study to examine these effects on people with metastatic melanoma. These late-stage skin cancer patients were undergoing immunotherapy with anti-PD-1 checkpoint inhibitors.
In these melanoma patients, taking over-the-counter probiotic supplements was associated with a 70% lower chance of response to cancer immunotherapy treatment with anti-PD-1 checkpoint inhibitors, according to the preliminary study.
Correlation or causation
The link is believed to be the lower diversity in the gut microbiome caused by probiotics, previously found to be associated with poorer immunotherapy response.
In recent years, scientists have discovered that the trillions of intestinal microbes that make up the gut microbiome exert significant control over the immune system. Cancer immunotherapy drugs such as checkpoint inhibitors work by engaging the immune system to fight off cancer.
In theory then, the makeup of the microbiome could affect the immune system, and in turn, the ability for immunotherapy to work against cancer. As immunotherapy is a new treatment that is showing much promise, any surrounding factors that increase the efficacy of the treatment would be a huge boost to sufferers, medical professionals and companies researching and producing them.
A prior study by Dr Wargo and Spencer in 2018 found that a more diverse array of microbes in the gut was associated with better response to checkpoint inhibitors for cancer. Certain types of bacteria in the Ruminococcaceae family were also associated with a better response to anti-PD-1 checkpoint inhibition, while other types, such as those in the order Bacteroidales, were linked to a poorer outcome.
Other influences
This is the first clinical study designed to examine the relationships between diet, the gut microbiome and immunotherapy response in cancer patients.
In addition to the probiotics findings, the data also showed patients response based on other gut influences:
- Patients who reported eating a high-fibre diet were five times as likely to respond to cancer immunotherapy
- Diets rich in whole grains had more bacteria associated with a positive response to checkpoint immunotherapy
- Diets high in processed meat and added sugar had fewer bacteria associated with a positive response to checkpoint immunotherapy
Using this to our advantage
While this study focused on correlations rather than the root cause, other randomised, controlled clinical trials are underway that are designed to directly answer the question of whether one can manipulate the microbiome – through food, faecal transplant or other means – to improve cancer immunotherapy response.
The Parker Institute is now conducting such a trial in collaboration with MD Anderson and Seres Therapeutics. This randomised, placebo-controlled clinical study is evaluating whether a specially designed oral microbiome pill with specific types of bacteria could positively impact a patient’s response to checkpoint inhibitors.
The tentative take-home of this study is the support of the concept of diet as a potential complementary treatment for immunotherapy. A game-changing notion.
