Text and Data Mining valid from 2019-07-31
Received: 7 January 2019
Accepted: 23 July 2019
First Online: 31 July 2019
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: 2017–437). It was determined to be a retrospective analysis of de-identified data, and thus was determined to be exempt from requiring written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.