Funding for this research was provided by:
Yantai Science and Technology Bureau (2020YD014)
Received: 27 April 2020
Accepted: 29 October 2020
First Online: 4 November 2020
Ethics approval and consent to participate
: Our study was exempted from institutional review board approval because of using the de-identified data in the SEER database.
: Not applicable.
: The authors declared that they had no competing interests.