Received: 27 June 2018
Accepted: 8 October 2018
First Online: 19 October 2018
Ethics approval and consent to participate
: All procedures were performed in accordance with the ethical standards of the institutional and/or national research committee and in line with the 1964 Declaration of Helsinki. This retrospective study was approved by the Medical Research Ethics Committee of Tokyo Medical and Dental University (D2015–600 (Previous number: No.1235)).
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.