Funding for this research was provided by:
1.3.5 Project for Disciplines of Excellence, West China Hospital, Sichuan University (ZYJC18007)
Received: 28 September 2020
Accepted: 28 December 2020
First Online: 12 January 2021
Ethics approval and consent to participate
: Not applicable. (This is a SEER database-based retrospective study. We signed a SEER Research Data Use Agreement form and gained access to data in SEER database. There is no need for SEER database-based study to obtain informed consent.)
: Not applicable.
: The authors declare that they have no competing interests.