Funding for this research was provided by:
National Research Foundation of Korea (NRF-2016R1D1A1B01014677)
Received: 24 September 2020
Accepted: 15 January 2021
First Online: 28 January 2021
Ethics approval and consent to participate
: The institutional review board of our university approved this retrospective study, and the requirement to obtain informed consent was waived (IRB approved no. 4-2016-0914).
: Not applicable
: The authors declare that they have no competing interests.