Funding for this research was provided by:
National Research Foundation of Korea (NRF-2018R1C1B5040610)
Received: 22 February 2020
Accepted: 15 April 2020
First Online: 17 April 2020
Ethics approval and consent to participate
: The study design was approved by the institutional review board of our institution (Registration number: 2020–01-038) and the requirement for informed consent was waived due to the retrospective nature of the study.
: Not applicable.
: The authors declare that they have no competing interests.