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, Istituto di Ricerche Farmacologiche Mario Negri IRCCS - Laboratory of Methodology of Systematic Reviews and Guidelines Production, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Fondazione IRCCS Istituto Nazionale dei Tumori - Head and Neck Medical Oncology Unit, Seeland Cancer Center, Fondazione IRCCS Istituto Nazionale dei Tumori, IRCCS Humanitas Research Hospital, University of Brescia, Humanitas University, Fondazione IRCCS Istituto Nazionale dei Tumori - Head and Neck Medical Oncology Unit and Humanitas University

Fondazione IRCCS Istituto Nazionale dei Tumori - Head and Neck Medical Oncology Unit, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, affiliation not provided to SSRN, University of Campania Luigi Vanvitelli, Ospedale Santa Chiara - Azienda Ospedaliero Universitaria Pisana, Fondazione Policlinico Universitario A. Gemelli IRCCS - COU of Dermatology, affiliation not provided to SSRN, affiliation not provided to SSRN, University of Trieste, Fondazione IRCCS Istituto Nazionale dei Tumori, IRCCS Ospedale Policlinico San Martino - Department of Medical Oncology, IRCCS Humanitas Research Hospital, University of Brescia, University of Trieste and University of Brescia - Medical Oncology Unit