Article History
Received: 31 October 2018
Accepted: 19 February 2019
First Online: 8 March 2019
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: The Institutional Review Board approved an exemption for this study due to its retrospective design (IRB No.: B-1808/484-106, Seoul National University Bundang Hospital Institutional Review Board).
: For this type of study, formal informed consent was not required.