Received: 8 February 2020
Accepted: 8 June 2020
First Online: 26 June 2020
Ethics approval and consent to participate
: This study was approved by the Ethics Committee of the Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences and Okayama University Hospital (approval number1906-024), and it was conducted in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1964 and later versions. Due to the retrospective nature of the study, the need for informed consent was waived.
: Not applicable.
: The authors declare that they have no competing interests.