Cohort Study of Secondary Endocrine Therapy in Metastatic Breast Cancer with a Poor Response to Initial Endocrine Therapy

Naruto Taira^1*, Tomomi Fujisawa², Kazuhiro Araki³, Takayuki Iwamoto¹, Kentaro Sakamaki⁴, Masato Takahashi, Tomohiko Aihara⁶ and Hirofumi Mukai⁷

¹Department of Breast and Endocrine Surgery, Okayama University Hospital, 2-5-1 Shikatacho, Okayama Kita-ku, Okayama, 700-8558, Japan, E-mail: ntaira@md.okayama-u.ac.jp

²Department of Breast Oncology, Gunma Prefectural Cancer Center, 617-1 Takahayashinishicho, Ota, Gunma, 373-8550, Japan, E-mail: ntaira@md.okayama-u.ac.jp

³Department of Breast Medical Oncology, The Cancer Institute Hospital, Japanese Foundation for Cancer Research, 3-8-1 Ariake, Koto-ku, Tokyo 135-8550, Japan, E-mail: ntaira@md.okayama-u.ac.jp

⁴Department of Biostatistics and Epidemiology, Yokohama City University Graduate School of Medicine, 4-57 Urafune, Minami-ku, Yokohama, Kanagawa, 232-0024, Japan, E-mail: ntaira@md.okayama-u.ac.jp

⁵Department of Breast Surgery, National Hospital Organization Hokkaido Cancer Center, 2-3-54 Kikusui 4-jo, Shiroishi-ku Sapporo-shi Hokkaido, 003-0804, Japan, E-mail: ntaira@md.okayama-u.ac.jp

⁶Breast Center, Aihara Hospital, 3-4-30, Makiochi, Minoh, Osaka, 562-0004, Japan, E-mail: ntaira@md.okayama-u.ac.jp

⁷Division of Breast and Medical Oncology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, Chiba, 277-8577, Japan, E-mail: ntaira@md.okayama-u.ac.jp

^*Corresponding Author: Naruto Taira, Department of Breast and Endocrine Surgery, Okayama University Hospital, 2-5-1 Shikatacho, Okayama Kita-ku, Okayama, 700-8558, Japan, Fax: 086-235-7269 Email: