PRISMA-RT is an association between of seventeen radiotherapeutic institutions that have decided to cooperate in the field of patient safety. The start-up for this cooperation was made by Mrs. Petra Reijnders and Mr. Huub Backes (Maastro Clinic) and Mr. Anne Joustra (Catharina hospital). The association has been established on April 10, 2008. The name ‘PRISMA-RT’ is an acronym for Prevention, Recovery and Information System for Monitoring and Analysis in RadioTherapy. The well known PRISMA-analysis method has been developed by Tjerk van der Schaaf and is the basis for this cooperation. It is therefore integrated in the name of association.