Received: 5 March 2020
Accepted: 7 April 2020
First Online: 24 May 2020
Ethics approval and consent to participate
: The Institutional Review Board (IRB) of Peking Union Medical College Hospital (PUMCH) reviewed the protocol. This is retrospective and meta-analysis study. The protocol is rational and scientific. The study accords with principle of ethics. The IRB thus approve the protocol. This is a retrospective study and written human subject consent was unnecessary.
: No applicable, as no individual patient data has been published.
: The authors have no conflict of interest to disclose.