title: Which threshold for ER positivity? a retrospective study based on 9639 patients.
abstract: BACKGROUND
  Guidelines for the use of chemotherapy and endocrine therapy recently recommended that estrogen receptor (ER) status be considered positive if ≥1% of tumor cells demonstrate positive nuclear staining by immunohistochemistry. In clinical practice, a range of thresholds are used; a common one is 10% positivity. Data addressing the optimal threshold with regard to the efficacy of endocrine therapy are lacking. In this study, we compared patient, tumor, treatment and survival differences among breast cancer patients using ER-positivity thresholds of 1% and 10%.
  
  
  METHODS
  The study population consisted of patients with primary breast carcinoma treated at our center from January 1990 to December 2011 and whose records included complete data on ER status. Patients were separated into three groups: ≥10% positive staining for ER (ER-positive ≥10%), 1%-9% positive staining for ER (ER-positive 1%-9%) and <1% positive staining (ER-negative).
  
  
  RESULTS
  Of 9639 patients included, 80.5% had tumors that were ER-positive ≥10%, 2.6% had tumors that were ER-positive 1%-9% and 16.9% had tumors that were ER-negative. Patients with ER-positive 1%-9% tumors were younger with more advanced disease compared with patients with ER-positive ≥10% tumors. At a median follow-up of 5.1 years, patients with ER-positive 1%-9% tumors had worse survival rates than did patients with ER-positive ≥10% tumors, with and without adjustment for clinical stage and grade. Survival rates did not differ significantly between patients with ER-positive 1%-9% and ER-negative tumors.
  
  
  CONCLUSIONS
  Patients with tumors that are ER-positive 1%-9% have clinical and pathologic characteristics different from those with tumors that are ER-positive ≥10%. Similar to patients with ER-negative tumors, those with ER-positive 1%-9% disease do not appear to benefit from endocrine therapy; further study of its clinical benefit in this group is warranted. Also, there is a need to better define which patients of this group belong to basal or luminal subtypes.
authors.affiliation: Department of Surgical Oncology.
authors.forename: M
authors.initials: M
authors.lastname: Yi
authors.forename: L
authors.initials: L
authors.lastname: Huo
authors.forename: K B
authors.initials: KB
authors.lastname: Koenig
authors.forename: E A
authors.initials: EA
authors.lastname: Mittendorf
authors.forename: F
authors.initials: F
authors.lastname: Meric-Bernstam
authors.forename: H M
authors.initials: HM
authors.lastname: Kuerer
authors.forename: I
authors.initials: I
authors.lastname: Bedrosian
authors.forename: A U
authors.initials: AU
authors.lastname: Buzdar
authors.forename: W F
authors.initials: WF
authors.lastname: Symmans
authors.forename: J R
authors.initials: JR
authors.lastname: Crow
authors.forename: M
authors.initials: M
authors.lastname: Bender
authors.forename: R R
authors.initials: RR
authors.lastname: Shah
authors.forename: G N
authors.initials: GN
authors.lastname: Hortobagyi
authors.forename: K K
authors.initials: KK
authors.lastname: Hunt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000145:classification / Q000378:metabolism* / Q000401:mortality / Q000628:therapy; D018270:Carcinoma, Ductal, Breast / Q000145:classification / Q000378:metabolism* / Q000401:mortality / Q000628:therapy; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000145:classification / Q000378:metabolism* / Q000401:mortality / Q000628:therapy; D017024:Chemotherapy, Adjuvant; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008875:Middle Aged; D016016:Proportional Hazards Models; D011960:Receptors, Estrogen / Q000378:metabolism*; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D011960:Receptors, Estrogen
keywords: breast cancer; estrogen receptor; low positive; survival