Funding for this research was provided by:
Grant-in-Aid for Scientific Research from the Ministry of Education and Science, Japan (B, No. 22390296)
National Cancer Center Research and Development Fund (28-A-16)
Received: 17 December 2018
Accepted: 24 June 2019
First Online: 4 July 2019
Ethics approval and consent to participate
: Approval for the present study was obtained from the Institutional Review Board of the JOA and National Cancer Center (2018–085). The requirement for informed consent was waived because of the anonymous nature of the data.
: Not applicable.
: The authors declare that they have no competing interests.