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Article History

Received: 12 September 2025

Accepted: 2 February 2026

First Online: 19 March 2026

Declarations

:

: Authors received support from Eisai for medical writing and the article processing charge for the submitted article. NM declared receiving grants/contracts (institution) from Chugai Pharmaceutical, Eli Lilly, AstraZeneca, Pfizer, Daiichi Sankyo, MSD, Eisai, Novartis, Gilead Sciences and Ono Pharmaceutical; honoraria (personal) from Chugai Pharmaceutical, Pfizer, AstraZeneca, Eli Lilly, Daiichi Sankyo, Eisai, Gilead Sciences and MSD; and serving as a representative of the Board of Directors (unpaid, 2021–2025) and as a member of the Board of Directors (unpaid, 2007–present) of Japan Breast Cancer Research Group (JBCRG), as a member of the Board of Directors (unpaid, 2021–2024) of Japanese Breast Cancer Society (JBCS), as a member of the Board of Directors (unpaid, 2023–present) of Japan Society of Clinical Oncology (JSCO), and as a member of the Board of Directors (unpaid, 2024–present) of Japan Association of Breast Cancer Screening (JABCS), and as a representative of the Board of Directors (unpaid, 2025–present) of Kyoto Breast Cancer Research Network (KBCRN). HB declared receiving honoraria for lectures (personal) from Chugai Pharmaceutical, Daiichi Sankyo, Eli Lilly, Eisai, Kyowa Kirin, AstraZeneca, Pfizer and MSD. TY declared receiving consulting fees (personal) from Daiichi Sankyo, Eli Lilly, and Pfizer; honoraria (personal) from AstraZeneca, Chugai Pharmaceutical, Daiichi Sankyo, Eisai, Eli Lilly, Gilead Sciences, Kyowa Kirin, Pfizer, and Taiho Pharmaceutical. HS declared receiving honoraria (personal) from Daiichi Sankyo, Chugai Pharmaceutical, Eli Lilly, Taiho Pharmaceutical, MSD, Eisai, Kyowa Kirin, Pfizer, and AstraZeneca. M (Takahashi) declared receiving honoraria for lectures (personal) from AstraZeneca, Eli Lilly, Daiichi Sankyo, MSD, Eisai, and Pfizer. SEN declared receiving honoraria (personal) from Pfizer, Eli Lilly, MSD, Chugai Pharmaceutical, Gilead Sciences, AstraZeneca, Daiichi Sankyo, and Eisai. TA declared receiving grants/contracts (personal) from Pfizer; honoraria (personal) from Pfizer, Chugai Pharmaceutical, AstraZeneca, Eli Lilly, Kyowa Kirin, MSD, and Daiichi Sankyo; receipt of equipment, materials, drugs, medical writing support, gifts, or other services from AstraZeneca, Mochida Pharmaceutical, and Pfizer. M (Tokiwa) declared receiving honoraria (personal) from Daiichi Sankyo. RN declared receiving honoraria (personal) from Chugai Pharmaceutical, Daiichi Sankyo, Eli Lilly, Medicone BD, AstraZeneca, Nippon Kayaku, Exact Sciences, and Kyowa Kirin. HI declared receiving grants/contracts (institution) from Eisai, Daiichi Sankyo, Chugai Pharmaceutical, Takeda Pharmaceutical, AstraZeneca, MSD, Ono Pharmaceutical, and Nipro; consulting fees (personal) from Mitsubishi Tanabe, AstraZeneca, and Asahi Kasei; honoraria (personal) from Eisai, Chugai Pharmaceutical, Pfizer, Kyowa Kirin, Daiichi Sankyo, Taiho Pharmaceutical, AstraZeneca, MSD, and Eli Lilly. SS declared receiving grants/contracts (institution) from Taiho Pharmaceutical, Eisai, Chugai Pharmaceutical, Takeda Pharmaceutical, MSD, AstraZeneca, Daiichi Sankyo, Gilead Sciences, Eli Lilly, and Sanofi; honoraria (personal) from Chugai Pharmaceutical, Kyowa Kirin, MSD, Novartis, Eisai, Takeda Pharmaceutical, Daiichi Sankyo, Eli Lilly, AstraZeneca, Pfizer, Taiho Pharmaceutical, Ono Pharmaceutical, Nippon Kayaku, Gilead Sciences, and Exact Sciences; participation on a Data Safety Monitoring Board or Advisory Board for Chugai/Roche, AstraZeneca, Eli Lilly, Pfizer, Kyowa Kirin, Daiichi Sankyo, and MSD; serving as an executive board member of JBCRG, JBCS, and Japanese Society of Medical Oncology (JSMO). SM declared receiving honoraria (personal) from AstraZeneca, Bristol Myers Squibb, Chugai Pharmaceutical, Eli Lilly, MSD, and Ono Pharmaceutical. M (Toi) declared receiving grants (institution) from Kansai Med Net, AFI technology, Eisai, Astellas, Nippon Kayaku, Taiho Pharmaceutical, Sanwa Syurui, Shimadzu, Chugai Pharmaceutical, Pfizer, Yakult, Zene, AstraZeneca, JBCRG, and Eisai; consulting fees (personal) from Bertis, Eli Lilly, and Daiichi Sankyo; honoraria (personal) from AstraZeneca, MSD, Eisai, Devicor Medical Japan, Kyowa Kirin, Daiichi Sankyo, Eli Lilly, Nippon Kayaku, Taiho Pharmaceutical, Exact Sciences, Shimadzu, Chugai Pharmaceutical, Pfizer, Yakult, and Sysmex; serving as a chairman (unpaid) for JBCS and a member of the Board of Directors of JBCRG and KBCRN; as an associate editor for Breast Cancer Research and Treatment, Science Reports and Cancer Science. HY, MI, SI, HK, and HH declared no conflicts of interest related to the work.

: The study was conducted in accordance with the Declaration of Helsinki and the Ethical Guidelines for Clinical Research of the Ministry of Health, Labour and Welfare of Japan. The study protocol was reviewed and approved by the institutional review board of each participating institution upon study initiation.

: All patients provided informed consent to participate in the JBCRG-22 study. Additional consent for data to be collected from their medical records and included in the present analysis was considered unnecessary, because no further interventions were involved.

: Not applicable.