How does the gut microbiome affect the success of cancer treatment?

The human gut microbiome contains about 44 billion microbes, ten times the number of cells in our body. It is a complex and diverse ecosystem that plays a crucial role in the functioning of the entire body. A balanced and diverse microbiota could be the key to successful cancer therapy," experts say.

According to recent studies, fecal microbiota transplantation can restore and balance the microflora of cancer patients. This can then have a significant impact on the effectiveness of cancer treatment. Experts shared new therapy recommendations, emphasizing special nutrition to restore gut microbiota.

Microbial diversity is key to successful therapy

If the microbiome is out of balance, intestinal dysbiosis occurs, which exceeds the risk of systemic diseases," notes Hendrik Poeck, MD, Chief Physician of Internal Medicine at the University Hospital Regensburg. According to the researcher, this also affects cancer and its treatment methods.

"Microbial diversity influences whether a tumor will grow, whether it leads to inflammation, immune response mechanisms or genomic instability, as well as the development of therapeutic resistance," says Poeck.

According to the expert, microbial diversity may also be useful for cancer treatment. The composition of the microbiome varies considerably from host to host and can mutate. These properties allow it to be used as a biomarker for predicting various physical responses and developing individualized diets.

How is the microbiome linked to disease mechanism?

The gut microbiome has a protective function, especially when the body is exposed to the external environment: in the epidermis and internal mucous membranes, in the gastrointestinal tract, in the lungs, thorax, and genitourinary system.

Clinical studies in humans and experiments in mouse models of cancer haveshown: certain microorganisms can have both protective and detrimental effects on cancer development, disease progression, and response to therapy.

Disturbances of the gut microflora that occur during antibiotic therapy can significantly affect a patient's response to immunotherapy. According to recent data, antibiotic administration before or after initiation of immune checkpoint inhibitor (ICI) therapy significantly affected both overall survival and progression-free survival.

ICI drugs also affect the gut microbiome and reduce response to immunotherapy. This effect was demonstrated by a new 2023 study that analyzed data from more than 2,700 cancer patients.

Another 2018 study showed that the effectiveness of ICI therapy was influenced by the bacterium Akkermansia muciniphila in the intestines of cancer patients. Considering this factor, the researchers did stool microbiota transplantation in mouse models.

The microbiome and the efficacy of immunotherapy

French scientists at the National Institute of Health and Medical Research, led by Laurence Zitvogel, MD, decided to find out: can the composition of the gut microbiota with the presence of the bacterium A muciniphila predict the efficacy of ICI immunotherapy?

The study involved 338 patients with non-small cell lung cancer. Researchers examined the prognostic value of fecal A muciniphila bacteria - "Akkerman status." Survival at low Akk was 13.4 months compared to 18.8 months at high Akk after treatment.

"These results are promising, but there is no one-size-fits-all solution. No conclusions about treatment efficacy can be drawn from a single bacterium, as all bacteria are crucial," notes Poeck.

TFM: a new perspective for cancer therapy

Fecal microbiota transplantation (TFM) is a relatively new procedure that can restore a healthy gut microbiome. Studies have shown the effectiveness of TFM in treating 20 patients with advanced-stage melanoma with ICI.

Seven days after applying TFM, the patients underwent immunotherapy treatment, which amounted to 3-4 cycles. After 12 weeks, most had complete or partial remission.

Despite such promising results, experts caution: TFM has a risk of sepsis of dangerous infections, which has prompted the FDA to require expanded screening of donor feces. Nevertheless, experts say the intervention is promising.

Dietary supplements and nutrition

Experts urge caution when taking probiotics. These products typically contain only a few types of bacteria, such as Lactobacillus spp and Bifidobacterium spp. "Over-the-counter probiotics may even delay microbiome recovery after taking antibiotics," Poech states, citing the study.

The researchers recommend enriching the diet with prebiotics - foods high in fiber - because they break down into short-chain fatty acids, promoting microbiota growth.

According to a 2021 study, just 20 g of fiber-rich foods had a significant impact on progression-free survival in 128 melanoma patients who received immunotherapy. The most significant benefit was seen in patients with adequate fiber intake who were not taking probiotics.

Citing Onkopedia's post-cancer diet aryrecommendations and the German Nutrition Society's10 rules of nutrition, the researchers emphasize the importance of a diet rich in plant fiber, moderate meat consumption, and avoiding artificial sweeteners, flavorings, and convenience foods. Along with a healthy diet, regular physical activity is equally important," the experts say.