First Online: 11 February 2020
Compliance with Ethical Standards
: This study received no funding.
: Takamasa Ohki has received speaking fees from Bayer Yakuhin and Eisai Pharmaceutical Co., Ltd. The other authors have nothing to disclose.
: Formal consent was not required for this type of study. The protocol was approved by the Institutional Ethics Committee of Mitsui Memorial Hospital. A retrospective analysis of records stored in a database was performed, and approval was obtained from the Ministry of Health and Welfare, Japan. All procedures complied with the Declaration of Helsinki.
: Written informed consent was obtained from all patients when they began treatment, but was not required for the analyses presented herein because this was a retrospective study.