Article History
Received: 21 July 2019
Accepted: 9 October 2019
First Online: 14 October 2019
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. We obtained the authorization to access the SEER database, with the number 14260-Nov2016.
: The SEER database does not reveal patient privacy, so patient informed consent is not required.