title: Proportion of estrogen or progesterone receptor expressing cells in breast cancers and response to endocrine therapy.
abstract: Immunohistochemical determination of ER/PR status has been the gold standard in clinical practice of breast cancer for decades. A cut-off of '1%' is commonly used; however, this is not supported by strict evidence. How the proportion of ER/PR-positive cells influences the response to endocrine therapy has been scarcely reported, either. To address these issues, 486 and 663 invasive breast cancer cases treated with or without adjuvant tamoxifen respectively (median follow-up period, 12.8 years) were enrolled, and effect of tamoxifen treatment was compared among ER/PR-positive or -negative groups immunohistochemically determined using various cut-offs. Tamoxifen significantly improved 5 years disease-free survival in ER/PR-positive, but not in ER/PR-negative, cases even using immunohistochemical >0% cut-off. Cases with ≥67% ER/PR expressing cells responded to tamoxifen by far the best. Patients having tumors without any ER/PR-positive cells should be excluded from endocrine therapy, whereas this therapy should be strongly recommended for those with ≥67% ER/PR-positive cells.
authors.affiliation: Research Team for Geriatric Pathology, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashi-ku, Tokyo 173-0015, Japan; Department of Pathology, Cancer Institute, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550, Japan. Electronic address: nhonma@tmig.or.jp.
authors.forename: Naoko
authors.initials: N
authors.lastname: Honma
authors.affiliation: Department of Pathology, Cancer Institute, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Horii
authors.affiliation: Breast Oncology Center, Cancer Institute Hospital, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550, Japan.
authors.forename: Takuji
authors.initials: T
authors.lastname: Iwase
authors.affiliation: Department of Target Therapy Oncology, Kyoto University Graduate School of Medicine, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Shigehira
authors.initials: S
authors.lastname: Saji
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Texas Medical School at Houston, 6431 Fannin, MSB 2.270, Houston, TX 77030, USA.
authors.forename: Mamoun
authors.initials: M
authors.lastname: Younes
authors.affiliation: Breast Medical Oncology, Breast Oncology Center, Cancer Institute Hospital, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Pathology, Cancer Institute, 3-8-31 Ariake, Koto-ku, Tokyo 135-8550, Japan.
authors.forename: Futoshi
authors.initials: F
authors.lastname: Akiyama
mesh_terms: D002288:Adenocarcinoma, Mucinous / Q000188:drug therapy / Q000378:metabolism*; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D018270:Carcinoma, Ductal, Breast / Q000188:drug therapy / Q000378:metabolism*; D018275:Carcinoma, Lobular / Q000188:drug therapy / Q000378:metabolism*; D017024:Chemotherapy, Adjuvant; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008408:Mastectomy; D011379:Prognosis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*; D012189:Retrospective Studies; D013629:Tamoxifen / Q000627:therapeutic use; D016896:Treatment Outcome
chemical_list: D018931:Antineoplastic Agents, Hormonal; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D013629:Tamoxifen; C508053:ERBB2 protein, human
keywords: Breast cancer; Cut-off; Endocrine therapy; Estrogen receptor; Immunohistochemistry; Progesterone receptor