Received: 1 October 2020
Accepted: 4 December 2020
First Online: 11 December 2020
Ethics approval and consent to participate
: This study was approved by the Institutional Research Ethics Committee of Sapporo Medical University. Informed consent was waived because of the retrospective nature of the study.
: Not applicable.
: YM received lecture fees from MSD K.K. and Japan Blood Product, and an industry-academia collaborative research grant from JIMRO Co., Ltd. HT received lecture fees from TSUMURA & CO. The other authors declare that they have no competing interests.