Fecal Microbiota And Metabolites In Head And Neck Cancer Patients Receiving (Chemo)Radiotherapy

This clinical study investigates whether the composition of the fecal microbiome and selected bacterial metabolites are associated with the efficacy and acute toxicity of radiotherapy in patients with locally advanced head and neck cancer treated with radical (chemo)radiotherapy. Increasing evidence suggests that gut bacteria and their metabolites may influence treatment response and side effects of cancer therapies, including radiotherapy. Participants will receive standard radical radiotherapy with or without concomitant chemotherapy according to clinical guidelines. During the course of treatment, participants will provide two stool samples and two blood samples. Stool samples will be collected at home and delivered to the hospital on the day of radiotherapy. Blood samples (7 ml) will be collected during routine clinical blood draws. Samples will be analyzed to determine fecal microbiome composition using 16S rRNA sequencing and quantification of butyrate-producing bacterial genes (buk and but), as well as concentrations of short-chain fatty acids and tryptophan metabolites using targeted metabolomics. Clinical outcomes will include treatment response assessed by CT or PET-CT imaging 3 months after completion of therapy, acute toxicity (CTCAE v5.0), and follow-up survival outcomes. The study aims to identify microbiome-related biomarkers that may contribute to improved personalization of supportive interventions in the future.