Influence of the microbiome on radiotherapy-induced oral mucositis and its management: A comprehensive review

Preventive effect of probiotics on oral mucositis induced by anticancer therapy: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Oral mucositis (OM) is a prevalent and painful complication in patients undergoing anticancer treatment, which significantly impacts patients' quality of life (QoL) and adherence to therapy. The use of oral probiotics as a preventive strategy for OM has shown promise, but the clinical evidence remains inconclusive. This meta-analysis of randomized controlled trials (RCTs) aims to evaluate the efficacy of probiotics in preventing OM caused by radiotherapy and/or chemotherapy.

METHODS

A comprehensive search of PubMed, EMBASE, Web of Science, Cochrane Library, and ClinicalTrials.gov was conducted up to January 31, 2024, to identify eligible RCTs. The primary outcomes were the incidences of severe OM and all-grade OM. Secondary outcomes included rates of anticancer treatment completion, clinical response, requirement for enteral nutrition, time course of OM, body weight loss, QoL, and adverse events (AEs). Risk ratios (RRs) with 95% confidence intervals (CIs) were calculated.

RESULTS

A total of 12 RCTs involving 1,376 patients were included in the quantitative analysis. Probiotics administration significantly reduced the risk of severe OM (RR = 0.61, 95%CI: 0.53-0.72, P < 0.001) and all-grade OM (RR = 0.90, 95%CI: 0.82-0.98, P = 0.016) compared to the control group. Multi-strain probiotics formulations were more effective than single-strain probiotics in preventing severe OM (P = 0.011). There were no significant differences between the probiotics and control groups regarding anticancer treatment completion (RR = 1.03, 95%CI: 0.98-1.08, P = 0.198), clinical response to therapy (RR = 1.05, 95%CI: 0.94-1.17, P = 0.406), or the need for enteral nutrition (RR = 1.28, 95%CI: 0.49-3.35, P = 0.680). AEs related to probiotics were rare, with no serious AEs attributable to probiotics use.

CONCLUSIONS

Oral probiotics are both safe and effective in preventing and reducing the severity of OM in patients undergoing anticancer therapy. Multi-strain probiotics demonstrate superior efficacy compared to single-strain probiotics. Further research is warranted to confirm these findings and optimize probiotic treatment strategies for cancer patients.

The prevalence of oral mucositis after radiotherapy in patients with Head and Neck Cancer and its associated factors: a meta-analysis

OBJECTIVES

Although the discussion about oral mucositis in Head and Neck Cancer (HNC) patients has become a prominent issue, its incidence and influencing factors have not been thoroughly synthesized. This meta-analysis aims to integrate the prevalence and associated factors of radiation-induced oral mucositis among HNC patients.

METHODS

This study searched the following electronic databases: PubMed, the Cochrane Database, the Web of Science, EMBASE, CNKI, the Wanfang Database, and the VIP Database. The publication timeframe for the included studies ranged from January 2005 until January 2024. Two investigators used the NOS scale and AHRQ evaluation criteria for quality evaluation. All qualified studies and statistical analyses were conducted using RevMan 5.2 and Stata 17.0.

RESULTS

Thirty eligible studies were included in the analysis. The results show that the prevalence of radiation-induced oral mucositis in HNC patients was 94% [95% CI (89%, 98%)]. Furthermore, the prevalence of severe radiation-induced oral mucositis in HNC patients is 37% [95%CI (29%, 45%)]. Chemotherapy, smoking history, diabetes, oral PH ≤ 7.0, and alcohol consumption are the main risk factors for radioactive oral mucositis. In addition, BMI > 24.0 kg/m2, no use of antibiotics, and no use of oral mucosal protective agents are associated with radioactive oral mucositis.

CONCLUSIONS

This meta-analysis underscores a significantly high prevalence of radiation-induced oral mucositis in HNC patients. Establishing healthy lifestyle habits and maintaining a healthy oral environment are pivotal in preventing radiation-induced oral mucositis.

Updated perspectives on the contribution of the microbiome to the pathogenesis of mucositis using the MASCC/ISOO framework

Advances in the treatment of cancer have significantly improved mortality rates; however, this has come at a cost, with many treatments still limited by their toxic side effects. Mucositis in both the mouth and gastrointestinal tract is common following many anti-cancer agents, manifesting as ulcerative lesions and associated symptoms throughout the alimentary tract. The pathogenesis of mucositis was first defined in 2004 by Sonis, and almost 20 years on, the model continues to be updated reflecting ongoing research initiatives and more sophisticated analytical techniques. The most recent update, published by the Multinational Association for Supportive Care in Cancer and the International Society for Oral Oncology (MASCC/ISOO), highlights the numerous co-occurring events that underpin mucositis development. Most notably, a role for the ecosystem of microorganisms that reside throughout the alimentary tract (the oral and gut microbiota) was explored, building on initial concepts proposed by Sonis. However, many questions remain regarding the true causal contribution of the microbiota and associated metabolome. This review aims to provide an overview of this rapidly evolving area, synthesizing current evidence on the microbiota's contribution to mucositis development and progression, highlighting (i) components of the 5-phase model where the microbiome may be involved, (ii) methodological challenges that have hindered advances in this area, and (iii) opportunities for intervention.

Opioid Use and Gut Dysbiosis in Cancer Pain Patients

Opioids are commonly used for the management of severe chronic cancer pain. Their well-known pharmacological effects on the gastrointestinal system, particularly opioid-induced constipation (OIC), are the most common limiting factors in the optimization of analgesia, and have led to the wide use of laxatives and/or peripherally acting mu-opioid receptor antagonists (PAMORAs). A growing interest has been recently recorded in the possible effects of opioid treatment on the gut microbiota. Preclinical and clinical data, as presented in this review, showed that alterations of the gut microbiota play a role in modulating opioid-mediated analgesia and tolerability, including constipation. Moreover, due to the bidirectional crosstalk between gut bacteria and the central nervous system, gut dysbiosis may be crucial in modulating opioid reward and addictive behavior. The microbiota may also modulate pain regulation and tolerance, by activating microglial cells and inducing the release of inflammatory cytokines and chemokines, which sustain neuroinflammation. In the subset of cancer patients, the clinical meaning of opioid-induced gut dysbiosis, particularly its possible interference with the efficacy of chemotherapy and immunotherapy, is still unclear. Gut dysbiosis could be a new target for treatment in cancer patients. Restoring the physiological amount of specific gut bacteria may represent a promising therapeutic option for managing gastrointestinal symptoms and optimizing analgesia for cancer patients using opioids.

Quantifying periodontitis-associated oral dysbiosis in tongue and saliva microbiomes-An integrated data analysis

BACKGROUND

Periodontitis is primarily driven by subgingival biofilm dysbiosis. However, the quantification and impact of this periodontal dysbiosis on other oral microbial niches remain unclear. This study seeks to quantify the dysbiotic changes in tongue and salivary microbiomes resulting from periodontitis by applying a clinically relevant dysbiosis index to an integrated data analysis.

METHODS

The National Center for Biotechnology Information (NCBI) database was searched to identify BioProjects with published studies on salivary and tongue microbiomes of healthy and periodontitis subjects. Raw sequence datasets were processed using a standardized bioinformatic pipeline and categorized by their ecological niche and periodontal status. The subgingival microbial dysbiosis index (SMDI), a dysbiosis index originally developed using the subgingival microbiome, was computed at species and genus levels and customized for each niche. Its diagnostic accuracy for periodontitis was evaluated using receiver operating characteristic curves.

RESULTS

Four studies, contributing 328 microbiome samples, were included. At both species and genus levels, periodontitis samples had a higher SMDI, but the differences were only significant for subgingival biofilm and saliva (p < 0.001). However, SMDI showed good diagnostic accuracy for periodontitis status for all three niches (area under curve ranging from 0.76 to 0.90, p < 0.05). The dysbiosis index of subgingival biofilm was positively correlated with saliva consistently (p < 0.001) and with the tongue at the genus level (p = 0.036).

CONCLUSIONS

While the impact on the tongue microbiome requires further investigation, periodontitis-associated dysbiosis affects the salivary microbiome and is quantifiable using the dysbiosis index. The diagnostic potential of salivary microbial dysbiosis as a convenient periodontal biomarker for assessing periodontal status has potential public health and clinical applications.

PLAIN LANGUAGE SUMMARY

Periodontitis, a severe inflammation of the gums which causes bone loss, is a disease caused by an imbalance of good and bad bacteria under the gums. However, it is unclear how this bacterial imbalance in the gums affects the bacterial balance of other distinct parts of the mouth, such as the saliva and tongue. This study uses bacteria datasets of four previously published studies, contributing a total of 328 bacterial samples. The data were processed using a uniform data analysis workflow, and a bacterial score, the subgingival microbial dysbiosis index (SMDI), previously shown to capture periodontitis-associated bacteria imbalance, was calculated separately for samples from under the gums, the saliva, and the tongue. The SMDI was able to distinguish between health and periodontitis within each oral location, and in general, the scores were higher for periodontitis samples, though this difference was significant only for bacteria under the gums and in saliva. Saliva scores were also consistently correlated with bacteria under the gums. This study shows that periodontitis-associated bacterial imbalances are observed in oral locations beyond just under the gums, particularly the saliva. Thus, saliva bacteria may be used as a convenient biomarker for assessing gum disease, allowing for potential public health and clinical applications.

Oral Candida in post-radiotherapy patients with xerostomia/hyposalivation: A narrative review

OBJECTIVE

Head and Neck Cancer (HNC) patients receiving radiotherapy (RT) often suffer from xerostomia and/or hyposalivation. As saliva plays an important antimicrobial and cleansing roles, these patients are at higher risks of opportunistic infections. This narrative review aims to provide an overview of current evidence on oral Candida colonisation and infection in these patients.

METHODS

A literature review of clinical studies on oral Candida colonisation and candidiasis in HNC patients receiving radiotherapy/chemoradiotherapy was conducted.

RESULTS

Many clinical studies found high levels of Candida colonisation and a substantial proportion of post-RT HNC patients suffering from oropharyngeal candidiasis (OPC). Importantly, oral Candida could be a reservoir for life-threatening systemic infection in immunocompromised patients. The rising prevalence of non-albicans Candida species and drug-resistant infections has made identification of Candida species and antifungal susceptibility more important. Recent advances in oral microbiome and its interactions with Candida are discussed. This review also offers perspectives on limitations of current evidence and suggestions for future research.

CONCLUSION

Further research to better understand Candida carriage, microbiome, OPC, and xerostomia/hyposalivation post-RT would aid in devising a more comprehensive long-term management plan and novel therapeutic approaches for HNC patients to achieve the full benefits of RT while minimising side effects.

Mechanisms and Potential Clinical Implications of Oral Microbiome in Oral Squamous Cell Carcinoma

Microorganisms in the oral cavity are abundant in the human body. At present, more than 700 species of oral microorganisms have been identified. Recently, a lot of literature has indicated that the oral microbiota plays an important role in the occurrence, development, and prognosis of oral squamous cell carcinoma (OSCC) through various mechanisms. And researchers are now trying to utilize oral microbiota in cancer diagnosis and treatment. However, few articles systematically summarize the effects of oral microbes in the diagnosis, treatment, and disease outcomes of oral cancer. Herein, we made a summary of the microbial changes at cancerous sites and placed more emphasis on the mechanisms by which the oral microbiome promotes cancerization. Moreover, we aimed to find out the clinical value of the oral microbiome in OSCC.