Text and Data Mining valid from 2018-05-22
Received: 10 January 2018
Accepted: 13 May 2018
First Online: 22 May 2018
Ethics approval and consent to participate
: This study was approved by the ethics committee of Peking University Cancer Hospital & Institute (Permission number 2013KT35). Additional patient consent for this retrospective study was not required.
: The authors declare that they have no competing interests.
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