Received: 2 April 2019
Accepted: 3 June 2019
First Online: 13 June 2019
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of the Cancer Institute Hospital of Japanese Foundation for Cancer Research (Tokyo, Japan). The patients’ concern has not been needed because of the retrospective nature of the study.
: Not applicable.
: The authors declare that they have no competing interests.