Received: 12 February 2019
Accepted: 31 May 2019
First Online: 11 June 2019
Ethics approval and consent to participate
: This retrospective study was exempt from requiring ethics approval. Bavarian state law (Bayrisches Krankenhausgesetz/Bavarian Hospital Law §27 Absatz 4 Datenschutz (Dataprotection)) allows the use of patient data for research, provided that any person’s related data are kept anonymous. German radiation protection laws request a regular analysis of outcomes in the sense of quality control and assurance, thus in the case of purely retrospective studies no additional ethical approval is needed under German law.
: Not applicable.
: The Department of Radiation Oncology of the University Hospital, LMU Munich holds research agreements with Brainlab and Elekta.