Received: 8 April 2019
Accepted: 22 October 2019
First Online: 6 November 2019
Ethics approval and consent to participate
: Written informed consent was signed by all patients or their legally authorized representatives. The Institutional Review Board (IRB) of Peking Union Medical College Hospital (PUMCH) has reviewed the protocol of this manuscript and has determined that this study is exempt from full IRB review since it is a retrospective study.
: All authors have read and approved the submission of the final manuscript.
: The authors declare that they have no competing interests.