The Oral Microbiome as a Prognostic Tool in Oral Malignant and Premalignant Lesions and in Medication Related Osteonecrosis of the Jaw

Plain-language summary

Oral squamous cell carcinoma (OSCC) is the most common malignant tumor of the head and neck, and its incidence has increased in recent years. Extensive surgery with neck dissection and chemo/radio/ targeted therapy is the current treatment for OSCC, and despite great progress in chemotherapy, radiotherapy, and targeted therapy in the last three decades, the prognosis of OSCC is still poor due to aggressive local invasion and metastasis, which lead to recurrence. Postoperative tumor recurrence confers a poor prognosis in OSCC and a poor quality of life. The 5-year survival rate is over 90% in OSCC patients without recurrence and 30% in patients with recurrence, with a median survival of 76.8 months in patients without recurrence and 42.5 months in patients with recurrence . Therefore, it is important to identify biomarkers that may predict the postoperative recurrence of OSCC. Also, some of the OSCC are preceded by precursor lesions. In the oral cavity the most common lesions recognized as potentially malignant are leukoplakia and erythroplakia, but it is also apparent that as many as 50% of OSCC arise from apparently clinically normal mucosa. The prognostic significance of an individual lesion is difficult to determine. At present therefore, the gold standard for the assessment of oral potentially malignant lesions is microscopic evaluation of haematoxylin and eosin stained sections for the presence of architectural and cytological changes, which are generally referred to as oral epithelial dysplasia (OED). The human microbiome is defined as the collective genomes of the microbes (composed of bacteria, bacteriophages, fungi, protozoa and viruses) that live inside and on the human body, and there are approximately 10 microbes and 100 microbial genes for each human cell and gene respectively. With the advent of next generation sequencing technology, the Human Microbiome Project delineated the composition of healthy microbial communities associated to different body sites in healthy individuals, including the oral cavity \[Human microbiome consortium\]. As opposed to a normal (healthy) microbiome, a disrupted microbiome or dysbiosis represents the lack of equilibrium, and is hypothetically related to disease. Interestingly, the healthy oral microbiome shows relative intraindividual stability over time, suggesting that differences in microbiome profiles may serve as useful tools for the identification of disease states. The working hypothesis is that in OSCC patients, the oral microbiome is altered in comparison to healthy individuals and certain microbial signatures are characteristic of healthy versus disease. In addition, in precursor conditions, i.e., oral epithelial dysplasia (OED), a partial alteration in the composition of the microbiome may predict the progression to malignancy.Also, during treatment, it could be that specific microbial signatures are associated with incomplete eradication, tendency to local recurrence or metastatic potential.Correlations to local recurrence (LR), distant metastases (DM) or disease free survival (DFS) adjusted to clinicopathologic correlations will be sought. In this study, buccal mucosa samples will be collected from patients with OSCC, OED and from healthy individuals , after signing for informed consent, according to Helsinki protocol. Routine pathologic diagnosis will be performed by expert Pathology physicians in our center. Data will be correlated to demographic and clinical data obtained from medical records. This will be carried out in line with institutional ethical guidelines.

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