Funding for this research was provided by:
Shandong Provincial Medical and Health Development plan (2013WSA13018)
Natural Science Foundation of Shandong Province (ZR2014HL062)
Received: 5 August 2020
Accepted: 18 November 2020
First Online: 7 December 2020
Ethics approval and consent to participate
: Because the data was collected from the Surveillance, Epidemiology, and End Results (SEER), database, therefore it doesn’t involve ethical approval and consent to participate.
: Not applicable.
: We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.