Abstract
BACKGROUND: We explored the interaction between the oral microbiome and the development of radiation-induced mucositis in patients with head and neck squamous cell cancer (HNSCC) undergoing chemoradiotherapy (CRT). We prospectively studied the oral microbiome and compared it to healthy controls. Additionally, we compared patients with low-grade (LGM) vs. high-grade mucositis (HGM). METHODS: Ten HNSCC patients scheduled for CRT were included. Saliva samples were characterized prior to, during, and nine months after CRT using metagenomic sequencing. We similarly characterized samples from seven healthy controls. We assessed alpha and beta diversity and examined abundances at different taxonomic levels between (sub)groups. RESULTS: Patients exhibited significantly reduced alpha diversity compared to controls at all times (p ⟨ 0.05). Differential abundance of taxa between patients and controls was observed at baseline. In patients, the relative abundance of Staphylococcus aureus and Escherichia coli increased significantly during CRT. Capnocytophaga spp. was associated with the definitive CRT patients' subgroup. At baseline, two fungal families (Melampsoraceae and Herpotrichiellaceaea) were more abundant in patients who later developed HGM. No differentially abundant taxa were found between LGM vs. HGM during irradiation. CONCLUSION: Our findings support the hypothesis that CRT, as well as HNSCC itself, influences the composition of the oral microbiome. Microbial markers found in patients who later developed HGM should be evaluated using independent cohorts to qualify their specific biomarker potential.