Received: 29 March 2019
Accepted: 13 September 2019
First Online: 4 November 2019
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board (IRB) of Hanyang University Medical Center and was exempt from an IRB review because we used existing, publicly available data, and the information of the subjects could not be identified directly or through identifiers linked to the subjects (IRB file No. HYUN 2016-06-008-002). Informed consent was waived because we utilized a de-identified database which was opened to the public.
: Not applicable.
: YKS has received research grants from Bristol-Myers Squibb, Eisai, Pfizer, and JW Pharmaceutical. The other authors declare that they have no competing interests.