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Natsumeda has received honoraria from Novocure; Y. Sonoda has received honoraria from Eisai, Dai-ichi Sankyo, and Chugai and research grants from Astellas, Eisai, Otsuka, Dai-ichi Sankyo, Chugai, Tsumura, Bayer, Pfizer, Fuji-film, and HOYA PENTAX; K. Asano, Y. Yamashita, T. Ono, T. Beppu, K. Matsuda, M. Ichikawa, M. Kanamori, M. Matsuzaka, A. Kurose, K. Saito, K. Ogasawara, Y. Fujii, H. Shimizu, H. Ohkuma, C. Kitanaka, T. Kayama, and T. Tominaga have no conflict of interest to declare.","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Conflict of interest"}},{"value":"This study was conducted with the approval of the ethics committees of Hirosaki University Graduate School of Medicine (2018-118) and individual institutions. In addition, since this was a retrospective study, notifications to patients to opt-out were given on the homepage of each hospital.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Ethical approval"}},{"value":"The institutional review board waived the requirement for informed consent, owing to the retrospective nature of the study. However, the details of the study are posted on the hospital\u2019s homepage (\n                      \n                      ).","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Consent to participate"}},{"value":"Not applicable.","order":5,"name":"Ethics","group":{"name":"EthicsHeading","label":"Consent for publication"}}]}}