1. Proton Therapy Unit, Department of Oncology, Azienda Provinciale per I Servizi Sanitari (APSS), Trento, Italy
2. Department of Radiation Oncology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Regina Elena National Cancer Institute, Rome, Italy
3. Proton Therapy Center, Delft, the Netherlands
4. Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
5. Department of Management and Law, Tor Vergata University of Rome, Rome, Italy
6. Centre for Organisational Research, Health and Public Management, Università della Svizzera Italiana (USI), Lugano, Switzerland
7. Department of Radiation Oncology, Gustave Roussy Cancer Campus, Villejuif, France