The importance of gut health and its role in chronic disease management has become more widely acknowledged in recent years, with an increase in the number of studies focusing on the gut microbiome and the role it plays in chronic disease and inflammation (Durack and Lynch, 2019).
With advances in the understanding of the part the gut microbiome plays in cancer, this article aims to explore the nurse's role in patient education in this area.
The gut microbiome
A microbiota is a collection of micro-organisms found in a particular environment such as on the skin or in the gut, whereas microbiome is a term to describe the collection of micro-organisms, the microbial structural elements, metabolites, and their habitat (Hou et al, 2022).
Within each human gut (comprising the small and large intestine) there are trillions of microscopic micro-organisms, made up of bacteria, viruses, parasites and fungi. The daily function of the body is supported by different species of microbes, most of which can be found within the gut. The gut microbiome is as unique as the individual; with the microbe population set at birth by DNA and later influenced by environmental factors such as diet (The Nutrition Source, 2024).
Our understanding of the important role the microbiome plays within the body, such as regulating inflammation, supporting the immune system and mediating certain metabolic processes, is increasing. Researchers, such as Hanson and Barber (2021), have described the microbiome as an independent organ due to the essential role it plays.
The gut microbiome and cancer
Cancer formation is multifactorial in nature; however, it is becoming clear that there is a relationship between the gut microbiome and cancer formation and links between the gut microbiome and the efficacy of systemic anti-cancer therapy (SACT) (Agagündüz et al, 2023). Our understanding of the anti-cancer potential of a healthy, diverse microbiome is growing, with emerging evidence of the influence gut health has on certain anti-cancer treatments, particularly within immunotherapy (Li et al, 2022).
Immunotherapy in cancer
It is widely understood that the expression of programmed death ligand (PD-L1) can often be upregulated in cancer cells, which makes them a potentially targetable expression. The combined positive score (CPS) and PD-L1 values are now established markers that can be indicative of the response to certain SACTs, such as immune checkpoint inhibitors (ICIs) (Fundytus et al, 2021).
To further understand the use of ICIs in cancer, it is important to have an overview of normal immune checkpoint regulation and the role of T cells (Cleveland Clinic, 2023).
T cells are created in the bone marrow before moving into the thymus for maturation. Mature T cells then migrate around the body and primarily ensure immune homeostasis. T cells can be grouped into naïve T cells, which can react to new pathogens, and memory T cells, which respond to pathogens to which an individual has already been exposed (Kumar et al, 2018).
ICIs bind to proteins on a healthy cell to signal to T cells that the cell is healthy and does not need to be killed. However, in cancer, tumours have been found to exhibit immunosuppressive signalling factors that fool the immune checkpoints into thinking that a cancerous cell is a healthy cell and does not need to be destroyed (Lao et al, 2022). In short, ICIs reduce immune checkpoint regulation, which allows T cells to recognise and actively destroy cancer cells (National Cancer Institute (NCI), 2022).
ICIs and the role of the gut microbiome
A systematic review by Zeriouh et al (2023) looked at 18 qualifying studies, involving a total of 775 patients, across four cancer types: metastatic melanoma, non-small-cell lung carcinoma, metastatic renal cell carcinoma and gastrointestinal cancer. This identified a direct correlation between certain microbiota species, ICI responders and non-responders. This demonstrated the importance of diversifying the gut microbiota, especially within this patient demographic.
The CheckMate 078 and CheckMate 870 trials reviewed enrolled individuals' gut microbiome diversity (taxonomic signature) at baseline and then measured response to PD-L1, finding that taxonomic signatures (specific levels of individual microbiota in combination) could be used to predict the response to ICIs (Wu et al, 2019; Lu et al, 2022; Cheng et al, 2022). The use of taxonomic signatures to predict outcomes in advanced cancer is further supported by Salosensaari et al (2021) who cite taxonomic signatures as a potential predictive tool for mortality risk.
The cancer patient experience
With research revealing the potential to directly improve ICI efficacy, patient experience and mortality rates, it is vital that health professionals empower patients and offer some practical guidance to diversifying their gut microbiome.
From a patient perspective, the lack of perceived control after being diagnosed with cancer (especially when the cancer has metastasised) is recognised to lead to poorer patient experience; both physiological and psychological (Rodríguez-Prat et al, 2022). This could indicate that providing patients with education and tools to increase their perception of control, such as making dietary changes to diversify their microbiome, could lead to a better patient experience and ultimately, when considering the data discussed by Zeriouh et al (2023), the potential for a better chance of ICI response and disease control and/or remission.
The nurse's role
It is widely recognised that the scope of the nurse's role has developed over recent years, with higher expectations for an individual nurse's knowledge and skill set, as well as their importance within the multidisciplinary team (MDT) (Blanco-Fraile et al, 2022).
Within an oncology setting, SACT administration units are consultant led but predominantly nurse run and the importance of building a positive patient rapport when delivering complex information is paramount in creating a patient safety culture (Oakley and Ream, 2024).
The Nursing and Midwifery Council (2018) cite promotion of patient wellbeing as a core nursing principle, as well as patient empowerment. The importance of empowerment and provision of knowledge by the nursing team is further supported by Tuominen et al (2020) who conducted a thematic analysis of colorectal cancer patients' expectation of their nurses and identified positive patient empowerment as correlating directly to a positive patient experience. Education on the gut microbiome should be considered at pre-assessment and in ongoing interactions with cancer patients.
The gut microbiome and stress
Psychological stress and depression is recognised to be both promoted and regulated within the gut. The symbiotic nature of the gut microbiome is further evidenced with external stress having the ability to influence the microbiome. As such, individuals under stress can experience changes to appetite, nausea and affects on gut motility (Madison and Kiecolt-Glaser, 2019).
Chaphalkar (2023) described the psychological stress of a cancer diagnosis as having a negative effect on the gut microbiome. This can lead to increased fatigue, potential changes in treatment efficacy and changes in mood and quality of life. It is important to consider ways to manage stress in relation to supporting the microbiome.
Reducing stress in cancer patients
When holistically reviewing and managing patients within an oncological setting, the nurse needs to consider the psychosocial effects of the diagnosis itself, as well as signpost patients to access support (Lu, 2022). The following have been found to help patients cope with the psychological burden of a cancer diagnosis and treatment:
Eating for better gut microbiome diversity
Eating for the microbiome is all about diversifying what a person eats. Polyphenols (beneficial plant compounds) are mainly found in colourful fruit and vegetables, cereals, beans and coffee, as well as other natural sources. They are instrumental in developing a healthy gut microbiome, found to promote healthy microbiota growth and diversification of the microbiome, as well as reduce inflammation and they have anti-oxidant properties (Wang et al, 2022). There are also certain foods to avoid when considering looking after the microbiome (see Table 1).
| Gut microbiome-friendly foods | ||
|---|---|---|
| Food type | Example | Effect on gut microbiome |
| Fermented foods |
|
Weaver (2021) noted the value of fermented foods in increasing microbial diversity, and encouraged daily consumption |
| Nuts |
|
Many nuts have a range of health benefits, they are high in fibre, rich in omega 3 and there is a proven correlation to improvement of gut health with regular consumption (Creedon et al, 2020) |
| Polyphenol-rich foods |
|
Polyphenols are naturally found in certain foods and often give vegetables colour and taste; they have been found to support a healthy microbiome and reduce inflammation (Islam, 2023) |
| Oats |
|
Oats have been found to directly support the growth of good microbiota, additionally they are high in prebiotic fibres (Xu et al, 2021) |
| Legumes |
|
Kadyan et al (2022) describe legumes as a good source of prebiotic fibre, which means they positively influence the microbiome and support increased production of short chain fatty acids within the gut. Short chain fatty acids are beneficial as they lower inflammation in the gut and can help reduce the risk of chronic diseases such as diabetes (Quadram Institute, 2023) |
| Gut microbiome-unfriendly food types | ||
| Food type | Example | Effect on microbiome |
| Ultra-processed foods |
|
Unfortunately supermarket shelves are full of ultra-processed food products and there is a clear detrimental link between the gut microbiota and ultra-processed foods. Ultra-processed food consumption leads to alteration of the gut microbiome and increased inflammation within the gut, which has the potential to increase the risk of developing chronic conditions (Shi, 2019) |
| Sugar |
|
Sugar has been found to disrupt healthy microbiota and increase inflammation; consumption should be reduced where possible. Research shows high intakes of sugar are as bad for health as high intakes of alcohol. A high sugar intake can lead to reduced immunity and a higher risk of infections (Arnone et al, 2022) |
Probiotics and prebiotics
Probiotics are foods or supplements that contain live micro-organisms intended to maintain or improve the ‘good’ bacteria in the body. Prebiotics are foods that act as food for human microflora.
Probiotics are recognised to help modulate the gut microbiome by positively influencing gut microbiota and have benefit within many different inflammatory disease settings, such as irritable bowel disease, Crohn's disease and cancer, although the mode of action of probiotics is not yet fully understood (Latif et al, 2023).
Lee et al (2019) explored the use of Lactobacillus fermentum and its influence on cell apoptosis of colorectal cancer cells in 2D and 3D culture. Their findings indicated Lactobacillus fermentum to be useful in a colorectal cancer setting, with increased rates of cell apoptosis in this group.
Current research, mainly conducted in vitro, has identified the beneficial properties of probiotics in modulating the proliferation and apoptosis of cancer cells, including, gastric, colonic and myeloid leukaemia cells (Slizewska et al, 2020).
The difficulties in regulating the quality and content of prebiotics available over the counter, as well as identifying which strains are useful in what setting is discussed by Shrifteylik et al (2023). These limitations are also highlighted by Rodriguez-Arrastia et al (2021) who found that probiotics have a place within toxicity management and reduction for SACT patients. Probiotics have the potential to both influence disease formation and patient quality of life but more research is needed into their application within an oncology setting.
Conclusion
Understanding the influence of the gut microbiome on cancer formation, management and prevention helps informs nursing care. Having a simple toolbox of small dietary changes and stress reduction techniques that can be used to educate and empower patients will support provision of holistic nursing care within the ever-evolving field of oncology.