Text and Data Mining valid from 2019-03-15
Received: 17 October 2018
Revised: 1 January 2019
Accepted: 29 January 2019
First Online: 15 March 2019
Compliance with ethical standards
: The scientific guarantor of this publication is Siwei Zhang.
: The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.
: No complex statistical methods were necessary for this paper.
: Written informed consent was not required for this study.
: Institutional Review Board approval was obtained.
: • retrospective• prognostic study• performed at one institution