Received: 23 February 2021
Accepted: 29 April 2021
First Online: 11 May 2021
: Formal consent was waived because of the retrospective nature or this study, and which was approved by the Institutional Review Board (IRB). IRB at Seoul National University Hospital (No. C-2009-058-1155) approved the study. All individual-level data were anonymized and only available to authorized researchers. IRB approved and monitored safety and adequacy of data management. This study was performed in accordance with the Declaration of Helsinki.
: Not applicable.
: The authors declare no competing interests.