Received: 11 April 2018
Accepted: 27 July 2018
First Online: 20 September 2018
Ethics approval and consent to participate
: The institutional review board of Tokyo Metropolitan Bokutoh Hospital approved the study (institutional approval reference number 29–54), which complied with the tenets of the Declaration of Helsinki. The requirement of informed consent was waived, owing to the retrospective design of the study.
: Not applicable.
: The authors declare that they have no competing interests.
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