Received: 3 December 2020
Accepted: 12 March 2021
First Online: 30 March 2021
: The study was approved by the Institutional Review Board of Fukushima Medical University (No. 2020190) and the requirement for obtaining patients’ informed consent was waived because of retrospective study. All procedures in this study were performed in accordance with the ethical standards of the institutional and/or national research committee and the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Not applicable.
: The authors declare that they have no competing interests.