affiliation not provided to SSRN, University of Brescia, Fondazione IRCCS Istituto Nazionale dei Tumori - Head and Neck Medical Oncology Unit, Fondazione IRCCS Istituto Nazionale dei Tumori - Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori - Department of Research, affiliation not provided to SSRN, affiliation not provided to SSRN, King Hussein Cancer Center (KHCC), University Hospital of Bellvitge - Bellvitge Biomedical Research Institute (IDIBELL), Acibadem MAA University School of Medicine - Department of Radiation Oncology, University of Piemonte Orientale, University of Genova, Azienda Ospedaliero-Universitaria Careggi, Hospital Duran i Reynals (ICO) - Catalan Institute of Oncology, Kuwait Cancer Control Centre - Radiation Oncology Department, Azienda Ospedaliera-Universitaria Pisana, Thomas Jefferson University, Thomas Jefferson University, University of Giessen - Faculty of Medicine, University Hospital of Modena - Radiation Oncology Unit, University of Brescia, University of Brescia, Thomas Jefferson University Hospital, AOU Città della Salute e della Scienza di Torino, Autonomous University of Barcelona - Medical Oncology Department, Fondazione IRCCS Istituto Nazionale dei Tumori - Head and Neck Medical Oncology Unit, Fondazione IRCCS Istituto Nazionale dei Tumori and Humanitas University

University of Brescia - Medical Oncology Unit, Fondazione IRCCS Istituto Nazionale dei Tumori - Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori - Department of Research, University of Brescia - Medical Oncology Unit, King Hussein Cancer Center (KHCC), University Hospital of Bellvitge - Bellvitge Biomedical Research Institute (IDIBELL), Acibadem MAA University School of Medicine - Department of Radiation Oncology, University of Piemonte Orientale, University of Genova, Azienda Ospedaliero-Universitaria Careggi, Hospital Duran i Reynals (ICO) - Catalan Institute of Oncology, Kuwait Cancer Control Centre - Radiation Oncology Department, Azienda Ospedaliera-Universitaria Pisana, Thomas Jefferson University, Thomas Jefferson University, University of Giessen - Faculty of Medicine, University Hospital of Modena - Radiation Oncology Unit, Thomas Jefferson University, University of Brescia, University of Brescia, AOU Città della Salute e della Scienza di Torino, Autonomous University of Barcelona - Medical Oncology Department, Fondazione IRCCS Istituto Nazionale dei Tumori - Head and Neck Medical Oncology Unit, Fondazione IRCCS Istituto Nazionale dei Tumori - Head and Neck Medical Oncology Unit and Fondazione IRCCS Istituto Nazionale dei Tumori