Received: 28 March 2020
Accepted: 25 August 2020
First Online: 31 August 2020
Ethics approval and consent to participate
: We received permission from the National Cancer Institute, US to access the research data file in the SEER program (reference number 10013-Nov2019). Ethics approval was waived by Ethics Committee of First Affiliated Hospital of Wenzhou Medical University, as SEER data is publicly available and without specific identifiers.
: Not applicable.
: The authors declare that they have no competing interests.