Received: 1 October 2017
Accepted: 16 March 2018
First Online: 27 March 2018
Ethics approval and consent to participate
: This retrospective study was approved by the Institutional Review Board (IRB) of the National Cancer Center Hospital (IRB code: 2015–320). It was determined to be a retrospective analysis of de-identified data, and was determined to be exempt from requiring written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.
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