Funding for this research was provided by:
National Natural Science Foundation of China (81402167)
Received: 19 July 2019
Accepted: 7 November 2019
First Online: 15 November 2019
Ethics approval and consent to participate
: The Clinical Research Ethics Committee of Peking University Cancer Hospital and Institute approved the research and the written informed consent was waived because this was a retrospective and observational study.
: Not applicable.
: The authors declare that they have no competing interests.