Head and neck cancer patients commonly present with unresectable locoregionally advanced disease in which radiotherapy is the mainstay of curative-intent treatment albeit at the cost of substantial acute and late toxicity. Recently discovered mechanisms by which gut microbiota and its metabolites impact tumor's and normal tissue's response to radiotherapy offer new ways to improve the therapeutic index of radiotherapy in solid tumors.~COMRAD-HNSCC is a prospective study assessing the correlation between gut microbiota composition and its metabolites and the response to radiotherapy in patients with unresectable locoregionally advanced head and neck cancer. Stool and serum samples will be collected at the beginning and at the end of curative radiotherapy treatment. The composition of gut microbiota will be analysed by ribosomal DNA high-throughput amplicon sequencing of the DNA isolated from stool samples, whereas targeted metabolomics using liquid chromatography-mass spectrometry will be performed on stool and serum samples.~The long-term goal of this study is to deepen the understanding of the role of gut microbiome and its metabolites in efficacy and toxicity of radiotherapy in head and neck cancer, and provide a basis for subsequent exploration to increase therapeutic index by regulating gut microbiota.
Preclinical studies have shown that the response of solid tumors and normal tissues to radiotherapy can be regulated by gut microbiota and its metabolites. In this study, the composition of gut microbiota in patients with locally advanced head and neck cancers undergoing definitive radiotherapy will be analysed together with bacterial metabolites in stool and blood and a possible correlation with treatment outcome and treatment toxicity will be determined.