Funding for this research was provided by:
National Natural Science Foundation of China (81502442)
Received: 9 December 2018
Accepted: 30 July 2019
First Online: 14 August 2019
Ethics approval and consent to participate
: This study is approved by the Ethics Committee of the First Affiliated Hospital of Xi’an Jiaotong University. The access of SEER database was also acquired.
: Not applicable.
: The authors declare that they have no competing interests.