Funding for this research was provided by:
China Scholarship Council (201708080137)
Deutsche Forschungsgemeinschaft (Open Access Publishing)
Received: 16 April 2019
Accepted: 16 October 2019
First Online: 24 October 2019
Ethics approval and consent to participate
: No IRB approval was required because the SEER Database uses pseudonyms rather than real patient demographic data.
: The authors have consented to publication after having read the final manuscript.
: The authors declare that they have no competing interests.