Funding for this research was provided by:
International Cooperation Foundation Project of Shaanxi Province (2019KW-033)
Received: 21 December 2020
Accepted: 6 May 2021
First Online: 17 May 2021
: We received permission to access the research data file in the SEER program from the National Cancer Institute, US (reference number 18015-Nov2019). Approval was waived by the local ethics committee, as SEER data is publicly available and de-identified.
: Not applicable.
: All authors declared no conflicts of interest among them.