Received: 8 February 2020
Accepted: 2 June 2020
First Online: 6 August 2020
Ethics approval and consent to participate
: This retrospective data analysis was approved by the Institutional Review Board of Seoul National University (S-D20200007).
: Consent for publication was obtained from all participants.
: Buyanbileg Sodnom-Ish, Mi Young Eo, Truc Thi Hoang Nguyen, Myung Joo Kim, and Soung Min Kim declare that they have no competing interests.