Text and Data Mining valid from 2018-10-04
First Online: 4 October 2018
Compliance with Ethical Standards
: This study had no sources of funding.
: Yoshitaka Arase, Tatehiro Kagawa, Kota Tsuruya, Hirohiko Sato, Erika Teramura, Kazuya Anzai, Shunji Hirose, Ryuzo Deguchi, Koichi Shiraishi, and Tetsuya Mine declare that they have no conflict of interest.
: All data generated or analyzed during this study are included in this published article.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the Institutional Review Board for Clinical Research at Tokai University (no. 16R-242).
: As this was a retrospective study, formal consent was not required.