Text and Data Mining valid from 2019-08-19
Received: 13 December 2018
Accepted: 12 August 2019
First Online: 19 August 2019
Ethics approval and consent to participate
: Not applicable. (Published articles on SEER database analysis do not require Ethics approval and consent to participate).
: Not applicable. The need for informed consent was waived due to the retrospective nature.
: The authors declare that they have no competing interests.