Effects of intensity-modulated radiotherapy on human oral microflora

Dysbiosis linking periodontal disease and oral squamous cell carcinoma-A brief narrative review

An association between periodontal disease and oral squamous cell carcinoma (OSCC) has been recognized. However, there is no causal relationship between the two. The polymicrobial etiology of periodontal disease is confirmed, and so are the proven etiological factors for OSCC. Inflammation lies at the core of periodontal pathogenesis induced by the putative microbes. OSCC has inflammatory overtures in its pathobiology. Bacterial species involved in periodontal disease have been extensively documented and validated. The microbial profile in OSCC has been explored with no specific conclusions. The scientific reasoning to link a common microbial signature that connects periodontal disease to OSCC has led to many studies but has not provided conclusive evidence. Therefore, it would be beneficial to know the status of any plausible microbiota having a similarity in periodontal disease and OSCC. This brief review attempted to clarify the existence of a dysbiotic "fingerprint" that may link these two diseases. The review examined the literature with a focused objective of identifying periodontal microbial profiles in OSCC that could provide insights into pathogen commonality. The review concluded that there is great diversity in microbial association, but important bacterial species that correlate with periodontal disease and OSCC are forthcoming.

A Review of the Role of Oral Microbiome in the Development, Detection, and Management of Head and Neck Squamous Cell Cancers

The role of the microbiome in the development and propagation of head and neck squamous cell cancer (HNSCC) is largely unknown and the surrounding knowledge lags behind what has been discovered related to the microbiome and other malignancies. In this review, the authors performed a structured analysis of the available literature from several databases. The authors discuss the merits and detriments of several studies discussing the microbiome of the structures of the aerodigestive system throughout the development of HNSCC, the role of the microbiome in the development of malignancies (generally and in HNSCC) and clinical applications of the microbiome in HNSCC. Further studies will be needed to adequately describe the relationship between HNSCC and the microbiome, and to push this relationship into a space where it is clinically relevant outside of a research environment.

The Role of the Microbiome in Oral Squamous Cell Carcinoma with Insight into the Microbiome-Treatment Axis

Oral squamous cell carcinoma (OSCC) is one of the leading presentations of head and neck cancer (HNC). The first part of this review will describe the highlights of the oral microbiome in health and normal development while demonstrating how both the oral and gut microbiome can map OSCC development, progression, treatment and the potential side effects associated with its management. We then scope the dynamics of the various microorganisms of the oral cavity, including bacteria, mycoplasma, fungi, archaea and viruses, and describe the characteristic roles they may play in OSCC development. We also highlight how the human immunodeficiency viruses (HIV) may impinge on the host microbiome and increase the burden of oral premalignant lesions and OSCC in patients with HIV. Finally, we summarise current insights into the microbiome–treatment axis pertaining to OSCC, and show how the microbiome is affected by radiotherapy, chemotherapy, immunotherapy and also how these therapies are affected by the state of the microbiome, potentially determining the success or failure of some of these treatments.

Clinical update on head and neck cancer: molecular biology and ongoing challenges

Head and neck squamous cell carcinomas (HNSCCs) are an aggressive, genetically complex and difficult to treat group of cancers. In lieu of truly effective targeted therapies, surgery and radiotherapy represent the primary treatment options for most patients. But these treatments are associated with significant morbidity and a reduction in quality of life. Resistance to both radiotherapy and the only available targeted therapy, and subsequent relapse are common. Research has therefore focussed on identifying biomarkers to stratify patients into clinically meaningful groups and to develop more effective targeted therapies. However, as we are now discovering, the poor response to therapy and aggressive nature of HNSCCs is not only affected by the complex alterations in intracellular signalling pathways but is also heavily influenced by the behaviour of the extracellular microenvironment. The HNSCC tumour landscape is an environment permissive of these tumours' aggressive nature, fostered by the actions of the immune system, the response to tumour hypoxia and the influence of the microbiome. Solving these challenges now rests on expanding our knowledge of these areas, in parallel with a greater understanding of the molecular biology of HNSCC subtypes. This update aims to build on our earlier 2014 review by bringing up to date our understanding of the molecular biology of HNSCCs and provide insights into areas of ongoing research and perspectives for the future.

Detection of Microbiota in Post Radiation Sinusitis

OBJECTIVES

A shift in the microbiota of chronic rhinosinusitis has been described after radiotherapy to the sinonasal cavity and skull base. There is a paucity of literature characterizing the bacteriology of post radiation sinusitis using next-generation gene sequencing techniques. This study aims to describe and compare the microbial flora of rhinosinusitis after radiotherapy using both culture and molecular techniques for microbial DNA detection.

METHODS

The medical records of patients treated with external beam radiation for sinonasal, nasopharyngeal, or skull base malignancy were reviewed at a tertiary care facility. Patients' sinonasal cavities were swabbed for routine culture or brushed for molecular gene sequencing. Swab specimens were processed for standard microbial culture, and brush specimens were sent for gene sequencing at Micro GenX Laboratory (Lubbock, Texas, USA).

RESULTS

Twenty-two patients were diagnosed with chronic sinusitis after undergoing radiotherapy. Staphylococcus aureus was the most common organism identified by both culture and gene sequencing, followed by Pseudomonas aeruginosa. Several additional organisms were detected by gene sequencing that were not isolated by routine culture techniques. Gene sequencing identified pathogens differing from culture results in 50% of patients examined.

CONCLUSION

The bacteriology of post radiation sinusitis appears to resemble the microorganisms responsible for chronic sinusitis in healthy adults. Next generation gene sequencing techniques may reveal additional organisms responsible for sinusitis and provide complementary results that may impact the medical treatment of post radiation sinusitis.

The oral cavity microbiota: between health, oral disease, and cancers of the aerodigestive tract

Many studies show that the human microbiome plays a critical role in the chronic pathologies of obesity, inflammatory bowel diseases, and diabetes. More recently, the interaction between cancer and the microbiome has been highlighted. Most studies have focused on the gut microbiota because it represents the most extensive bacterial community, and the body of evidence correlating it with gut syndromes is increasing. However, in the strict sense, the gastrointestinal (GI) tract begins in the oral cavity, and special attention should be paid to the specific flora of this cavity. This study reviewed the current knowledge about the various microbial ecosystems of the upper part of the GI tract and discussed their potential link to carcinogenesis. The overall composition of the microbial communities, as well as the presence or absence of "key species", in relation to carcinogenesis is addressed. Alterations in the oral microbiota can potentially be used to predict the risk of cancer. Molecular advances and the further monitoring of the microbiota will increase our understanding of the role of the microbiota in carcinogenesis and open new perspectives for future therapeutic and prophylactic modalities.

Head and neck intensity modulated radiation therapy leads to an increase of opportunistic oral pathogens

OBJECTIVES

The introduction of intensity modulated radiation therapy (IMRT) has led to new possibilities in the treatment of head and neck cancer (HNC). Limited information is available on how this more advanced radiation technique affects the oral microflora. In a prospective study we assessed the effects of various advanced treatments for HNC on the oral microflora, as well as the effects of elimination of oral foci of infection.

MATERIALS AND METHODS

All consecutive dentate patients >18years, diagnosed with a primary oral or oropharynx carcinoma and seen for a pre-treatment dental screening (May 2011-May 2013) were included. Patients were grouped by oncologic treatment: surgery (SURG), IMRT (IMRT) or IMRT+chemotherapy (CHIMRT). Dental screening data, demographic data, subgingival biofilm samples, oral lavages and whole saliva samples were obtained to microbiologically analyze the effects of cancer treatments (1-year follow-up).

RESULTS

This study included 82 patients (29 SURG, 26 IMRT and 27 CHIMRT). The trends in changes in prevalence and proportions of microorganisms were comparable in the IMRT and CHIMRT group. However, relative to the SURG group, increased prevalence of enteric rods, staphylococci and Candida species was observed in the IMRT and CHIMRT groups. In these groups, elimination of oral foci decreased the frequency of detection of pathogens such as Porphyromonas gingivalis, Tannerella forsythia and Streptococcus mutans.

CONCLUSION

Different treatments in HNC patients result in different changes in the oral microflora. Opportunistic pathogens such as staphylococci, enteric rods and Candida sp. tend to increase in prevalence after IMRT with or without chemotherapy, but not after surgical intervention.

Low-dose irradiation affects the functional behavior of oral microbiota in the context of mucositis

The role of host-microbe interactions in the pathobiology of oral mucositis is still unclear; therefore, this study aimed to unravel the effect of irradiation on behavioral characteristics of oral microbial species in the context of mucositis. Using various experimental in vitro setups, the effects of irradiation on growth and biofilm formation of two Candida spp., Streptococcus salivarius and Klebsiella oxytoca in different culture conditions were evaluated. Irradiation did not affect growth of planktonic cells, but reduced the number of K. oxytoca cells in newly formed biofilms cultured in static conditions. Biofilm formation of K. oxytoca and Candida glabrata was affected by irradiation and depended on the culturing conditions. In the presence of mucins, these effects were lost, indicating the protective nature of mucins. Furthermore, the Galleria melonella model was used to study effects on microbial virulence. Irradiated K. oxytoca microbes were more virulent in G. melonella larvae compared to the nonirradiated ones. Our data indicate that low-dose irradiation can have an impact on functional characteristics of microbial species. Screening for pathogens like K. oxytoca in the context of mucosits could be useful to allow early detection and immediate intervention.

Exploring the variation of oral microbiota in supragingival plaque during and after head-and-neck radiotherapy using pyrosequencing

OBJECTIVE

The aim of this article was to study the variation in oral microflora of the subgingival plaque during and after radiotherapy.

DESIGN

During and after radiotherapy, microbial samples were collected at seven time points (early stage, medium stage, and later stage of radiotherapy, and 1 month, 3 months, 6 months, and 1 year after radiotherapy) in three subjects for a total of 21 samples. Polymerase chain reaction (PCR) amplification was carried out on the 16S rDNA hypervariable V1-V3 region, and then the PCR products were determined by high-throughput pyrosequencing.

RESULTS

The rarefaction curve indicating the richness of the microflora demonstrated that the number of operational taxonomic units (OTUs) was in decline from the early stage of radiotherapy to the time point 1 month after radiotherapy and then trended upward. The Shannon diversity index declined during radiotherapy (ranging from 4.59 to 3.73), and generally rose after radiotherapy, with the lowest value of 3.5 (1 month after radiotherapy) and highest value of 4.75 (6 months after radiotherapy). A total of 120 genera were found; five genera (Actinomyces, Veillonella, Prevotella, Streptococcus, Campylobacter) were found in all subjects across all time points.

CONCLUSION

The richness and diversity of oral ecology decreased with increased radiation dose, and it was gradually restored with time.

Investigation of salivary function and oral microbiota of radiation caries-free people with nasopharyngeal carcinoma

Radiation caries have been reported to be correlated with radiotherapy-induced destruction of salivary function and changes in oral microbiota. There have been no published reports detailing patients who have remained radiation caries-free following radiotherapy for nasopharyngeal carcinoma. The aim of this study was to investigate the relationship between salivary function, oral microbiota and the absence of radiation caries. Twelve radiation caries-free patients and nine patients exhibiting radiation caries following irradiated nasopharyngeal carcinoma were selected. V40, the dose at which the volume of the contralateral parotid gland receives more than 40 Gy, was recorded. Stimulated saliva flow rate, pH values and buffering capacity were examined to assess salivary function. Stimulated saliva was used for molecular profiling by Denaturing Gradient Gel Electrophoresis. Mutans streptococci and Lactobacilli in saliva were also cultivated. There were no significant differences in V40 between radiation caries-free individuals and those with radiation caries. Compared with normal values, the radiation caries-free group had significantly decreased simulated saliva flow rate, while there were no significant differences in the saliva pH value and buffering capacity. Similar results were observed in the radiation caries group. There was no statistical difference in microbial diversity, composition and log CFU counts in cultivation from the radiation caries-free group and the radiation caries group. Eleven genera were detected in these two groups, among which Streptococcus spp. and Neisseria spp. had the highest distribution. Our results suggest that changes in salivary function and in salivary microbiota do not explain the absence of radiation caries in radiation caries-free individuals.

The oral microbiome diversity and its relation to human diseases

As one of the most clinically relevant human habitats, the human mouth is colonized by a set of microorganisms, including bacteria, archaea, fungi, and viruses. Increasing evidence has supported that these microbiota contribute to the two commonest oral diseases of man (dental caries and periodontal diseases), presenting significant risk factors to human health conditions, such as tumor, diabetes mellitus, cardiovascular diseases, bacteremia, preterm birth, and low birth weight in infants. It is widely accepted that oral microorganisms cause diseases mainly by a synergistic or cooperative way, and the interspecies interactions within the oral community play a crucial role in determining whether oral microbiota elicit diseases or not. Since a comprehensive understanding of the complex interspecies interactions within a community needs the knowledge of its endogenous residents, a plenty of research have been carried out to explore the oral microbial diversity. In this review, we focus on the recent progress in this field, including the oral microbiome composition and its association with human diseases.

Microbiota and their role in the pathogenesis of oral mucositis

Oral mucositis in patients undergoing cancer therapy is a significant problem. Its prevalence ranges between 20 and 100%, depending on treatment type and protocols and patient-based variables. Mucositis is self-limiting when uncomplicated by infection. Unfortunately, the incidence of developing a local or systemic infection during the course of the treatment is very high. At this stage, it is unclear which role oral microbiota play in the onset, duration, and severity of oral mucositis. Nevertheless, there is growing interest in this underexplored topic, and new studies are being undertaken to unravel their impact on the pathogenesis of mucositis.

Comparison of Dental Health of Patients with Head and Neck Cancer Receiving IMRT vs Conventional Radiation

Objective

To analyze the dental health of patients with head and neck cancer who received comprehensive dental care after intensity-modulated radiation therapy (IMRT) compared with radiation therapy (RT).

Study Design

Historical cohort study.

Setting

Veteran Affairs (VA) hospital.

Subjects and Methods

In total, 158 patients at a single VA hospital who were treated with RT or IMRT between 2003 and 2011 were identified. A complete dental evaluation was performed prior to radiation treatment, including periodontal probing, tooth profile, cavity check, and mobility. The dental treatment plan was formulated to eliminate current and potential dental disease. The rates of dental extractions, infections, caries, mucositis, xerostomia, and osteoradionecrosis (ORN) were analyzed, and a comparison was made between patients treated with IMRT and those treated with RT.

Results

Of the 158 patients, 99 were treated with RT and 59 were treated with IMRT. Compared with those treated with IMRT, significantly more patients treated with RT exhibited xerostomia (46.5% vs 16.9%; P < .001; odds ratio [OR], 0.24; 95% confidence interval [CI], 0.11-0.52), mucositis (46.5% vs 16.9%; P < .001; OR, 0.24; 95% CI, 0.11-0.52), and ORN (10.1% vs 0%; P = .014; OR, 0.07; 95% CI, 0.00-1.21). However, significantly more patients treated with IMRT were edentulous by the conclusion of radiation treatment (32.2% vs 11.1%; P = .002; OR, 3.8; 95% CI, 1.65-8.73).

Conclusion

Patients who were treated with IMRT had fewer instances of dental disease, more salivary flow, and fewer requisite posttreatment extractions compared with those treated with RT. The number of posttreatment extractions has been reduced with the advent of IMRT and more so with a complete dental evaluation prior to treatment.

Emerging evidence on the pathobiology of mucositis

BACKGROUND

Considerable progress has been made in our understanding of the biological basis for cancer therapy-induced mucosal barrier injury (mucositis). The last formal review of the subject by MASCC/ISOO was published in 2007; consequently, an update is timely.

METHODS

Panel members reviewed the biomedical literature on mucositis pathobiology published between January 2005 and December 2011.

RESULTS

Recent research has provided data on the contribution of tissue structure changes, inflammation and microbiome changes to the development of mucositis. Additional research has focused on targeted therapy-induced toxicity, toxicity clustering and the investigation of genetic polymorphisms in toxicity prediction. This review paper summarizes the recent evidence on these aspects of mucositis pathobiology.

CONCLUSION

The ultimate goal of mucositis researchers is to identify the most appropriate targets for therapeutic interventions and to be able to predict toxicity risk and personalize interventions to genetically suitable patients. Continuing research efforts are needed to further our understanding of mucositis pathobiology and the pharmacogenomics of toxicity.

Emerging evidence on the pathobiology of mucositis

BACKGROUND

Considerable progress has been made in our understanding of the biological basis for cancer therapy-induced mucosal barrier injury (mucositis). The last formal review of the subject by MASCC/ISOO was published in 2007; consequently, an update is timely.

METHODS

Panel members reviewed the biomedical literature on mucositis pathobiology published between January 2005 and December 2011.

RESULTS

Recent research has provided data on the contribution of tissue structure changes, inflammation and microbiome changes to the development of mucositis. Additional research has focused on targeted therapy-induced toxicity, toxicity clustering and the investigation of genetic polymorphisms in toxicity prediction. This review paper summarizes the recent evidence on these aspects of mucositis pathobiology.

CONCLUSION

The ultimate goal of mucositis researchers is to identify the most appropriate targets for therapeutic interventions and to be able to predict toxicity risk and personalize interventions to genetically suitable patients. Continuing research efforts are needed to further our understanding of mucositis pathobiology and the pharmacogenomics of toxicity.

Characterization of oral bacterial diversity of irradiated patients by high-throughput sequencing

The objective of this study was to investigate the compositional profiles and microbial shifts of oral microbiota during head-and-neck radiotherapy. Bioinformatic analysis based on 16S rRNA gene pyrosequencing was performed to assess the diversity and variation of oral microbiota of irradiated patients. Eight patients with head and neck cancers were involved in this study. For each patient, supragingival plaque samples were collected at seven time points before and during radiotherapy. A total of 147 232 qualified sequences were obtained through pyrosequencing and bioinformatic analysis, representing 3 460 species level operational taxonomic units (OTUs) and 140 genus level taxa. Temporal variations were observed across different time points and supported by cluster analysis based on weighted UniFrac metrics. Moreover, the low evenness of oral microbial communities in relative abundance was revealed by Lorenz curves. This study contributed to a better understanding of the detailed characterization of oral bacterial diversity of irradiated patients.

Exploring the dynamic core microbiome of plaque microbiota during head-and-neck radiotherapy using pyrosequencing

Radiotherapy is the primary treatment modality used for patients with head-and-neck cancers, but inevitably causes microorganism-related oral complications. This study aims to explore the dynamic core microbiome of oral microbiota in supragingival plaque during the course of head-and-neck radiotherapy. Eight subjects aged 26 to 70 were recruited. Dental plaque samples were collected (over seven sampling time points for each patient) before and during radiotherapy. The V1–V3 hypervariable regions of bacterial 16S rRNA genes were amplified, and the high-throughput pyrosequencing was performed. A total of 140 genera belonging to 13 phyla were found. Four phyla (Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria) and 11 genera (Streptococcus, Actinomyces, Veillonella, Capnocytophaga, Derxia, Neisseria, Rothia, Prevotella, Granulicatella, Luteococcus, and Gemella) were found in all subjects, supporting the concept of a core microbiome. Temporal variation of these major cores in relative abundance were observed, as well as a negative correlation between the number of OTUs and radiation dose. Moreover, an optimized conceptual framework was proposed for defining a dynamic core microbiome in extreme conditions such as radiotherapy. This study presents a theoretical foundation for exploring a core microbiome of communities from time series data, and may help predict community responses to perturbation as caused by exposure to ionizing radiation.