Received: 12 June 2020
Accepted: 9 September 2020
First Online: 16 September 2020
Ethics approval and consent to participate
: We received permission to access the research data file in the SEER program from the National Cancer Institute, US (reference number 15260-Nov2018). Approval was waived by the local ethics committee, as SEER data is publicly available and de-identified.
: Not applicable.
: The authors declare that they have no competing interests.