Funding for this research was provided by:
Clinical Capability Construction Project for Liaoning Provincial Hospitals (LNCCC-A01-2014)
Program of Education Department of Liaoning Province (L2014307)
National Key R&D Program of China (MOST-2016YFC1303200, MOST-2016YFC1303202)
Received: 6 December 2017
Accepted: 16 February 2018
First Online: 1 March 2018
Ethics approval and consent to participate
: Because the SEER-Medicare data are de-identified and are based on registry data, no prior informed consent was required. The access to the SEER-Medicare database was approved by the National Cancer Institute and Information Management Services, Inc. (D6-MEDIC-821), while this study was approved by the Institutional Review Board of the First Hospital of China Medical University.
: Not applicable.
: The authors declare that they have no competing interest.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.