Funding for this research was provided by:
National Cancer Center (NCC-1610200)
Received: 2 April 2018
Accepted: 27 July 2018
First Online: 8 August 2018
Ethics approval and consent to participate
: This study was reviewed and approved by the Ethics committee of National Cancer Center on 14 July 2017. The approval number is No. NCC2017–0167. We requested and obtained the cancer registration data (de-identified) used in this study from the Korea Central Cancer Registry (KCCR).
: Not applicable.
: The authors declare that they have no competing interests.
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