Received: 5 June 2019
Accepted: 27 September 2019
First Online: 14 November 2019
Ethics approval and consent to participate
: The institutional review board of Tokyo Metropolitan Bokutoh Hospital approved the study (institutional approval reference number 30-056), which complied with the tenets of the Declaration of Helsinki. The requirement for the acquisition of informed consent from patients was waived owing to the retrospective design of the study.
: Not applicable.
: The authors declare that they have no competing interests.