EGFR and cancer: Significant progress in understanding the molecular mechanisms of tumor response to irradiation enabled the development of a number of potential biomarkers for radiotherapy individualization in HNSCC, including epidermal growth factor receptor (EGFR) gene expression, DNA repair efficacy of cancer cells, tumor hypoxia and glucose uptake, human papillomavirus (HPV) status, and expression of CSC markers [7, 8, 23].