Received: 15 December 2020
Accepted: 2 July 2021
First Online: 17 July 2021
: The Institutional Review Board of Hokkaido University Hospital (No. 018–280) approved the present study. The committee did not require informed consent for this retrospective study. We put information of this study on Hokkaido University Hospital’s home page with the opportunity to opt out.
: Not applicable.
: The authors declare that they have no competing interests.