Funding for this research was provided by:
All Japan Labor Welfare Foundation
Received: 27 January 2021
Accepted: 30 March 2021
First Online: 16 April 2021
: We received permission from the National Cancer Institute, US to access the research data file in the SEER program (reference number 15602-Nov2019). Ethics approval was not applicable because SEER data is publicly available and without specific identifiers.
: Not applicable.
: No potential conflict of interest was reported by the authors.