Received: 20 September 2018
Accepted: 11 October 2018
First Online: 8 November 2018
Ethics approval and consent to participate
: This retrospective study based on four composite databases, which were all approved by the local research ethics committee. The processing of patients’ personal data was anonymized and complied with local data protection legislations. As no individual data is published as well as no intervention was performed to patients, the formal patient consent was waived.
: No applicable.
: The authors declare that they have no competing interests.
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