Recurrent or Metastatic Squamous Cell Carcinoma of Head and Neck

The main objective of this research is to increase the life expectancy of patients with advanced mouth and throat cancer, by adding avelumab to the standard TPEx treatment. All participants in this research will receive the same treatment which will take place in two phases: * 1st phase chemotherapy + immunotherapy: standard reference treatment (Docetaxel + cisplatin or carboplatin + cetuximab) * 2nd phase immunotherapy: cetuximab combined with avelumab which is the treatment under study.