title: A prospective comparison of ER, PR, Ki67 and gene expression in paired sequential core biopsies of primary, untreated breast cancer.
abstract: BACKGROUND
  Sequential biopsy of breast cancer is used to assess biomarker effects and drug efficacy. The preoperative "window of opportunity" setting is advantageous to test biomarker changes in response to therapeutic agents in previously untreated primary cancers. This study tested the consistency over time of paired, sequential biomarker measurements on primary, operable breast cancer in the absence of drug therapy.
  
  
  METHODS
  Immunohistochemistry was performed for ER, PR and Ki67 on paired preoperative/operative tumor samples taken from untreated patients within 2 weeks of each other. Microarray analysis on mRNA extracted from formalin fixed paraffin embedded cores was performed using Affymetrix based arrays on paired core biopsies analysed using Ingenuity Pathway Analysis (IPA) and Gene Set Analysis (GSA).
  
  
  RESULTS
  In 41 core/resection pairs, the recognised trend to lower ER, PR and Ki67 score on resected material was confirmed. Concordance for ER, PR and Ki67 without changing biomarker status (e.g. ER+ to ER-) was 90, 74 and 80 % respectively. However, in 23 paired core samples (diagnostic core v on table core), Ki67 using a cut off of 13.25 % was concordant in 22/23 (96 %) and differences in ER and PR immunohistochemistry by Allred or Quickscore between the pairs did not impact hormone receptor status. IPA and GSA demonstrated substantial gene expression changes between paired cores at the mRNA level, including reduced expression of ER pathway analysis on the second core, despite the absence of drug intervention.
  
  
  CONCLUSIONS
  Sequential core biopsies of primary breast cancer (but not core versus resection) was consistent and is appropriate to assess the effects of drug therapy in vivo on ER, PR and Ki67 using immunohistochemistry. Conversely, studies utilising mRNA expression may require non-treatment controls to distinguish therapeutic from biopsy differences.
authors.affiliation: St. Bartholomew's Hospital, Barts Health, London, UK.
authors.forename: Sirwan M
authors.initials: SM
authors.lastname: Hadad
authors.affiliation: Department of Pathology, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK.
authors.forename: Lee B
authors.initials: LB
authors.lastname: Jordan
authors.affiliation: Breast Unit, Churchill Hospital, Oxford, UK.
authors.forename: Pankaj G
authors.initials: PG
authors.lastname: Roy
authors.affiliation: Department of Pathology, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK.
authors.forename: Colin A
authors.initials: CA
authors.lastname: Purdie
authors.affiliation: Department of Breast and Endocrine Surgery, Okayama University, Okayama, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Iwamoto
authors.affiliation: Yale Medical Oncology, PO Box 208028, New Haven, 06520, CT, USA.
authors.forename: Lajos
authors.initials: L
authors.lastname: Pusztai
authors.affiliation: Department of Breast Medical Oncology, University of Texas MD Anderson Cancer Center, 1400 Holcombe Boulevard, Houston, 77030, TX, USA.
authors.forename: Stacy L
authors.initials: SL
authors.lastname: Moulder-Thompson
authors.affiliation: Department of Breast Surgical Oncology, University of Texas MD Anderson Cancer Center, 1400 Holcombe Boulevard, Houston, 77030, TX, USA. athompson1@mdanderson.org.
authors.forename: Alastair M
authors.initials: AM
authors.lastname: Thompson
keywords: Biomarkers; Breast cancer; Expression arrays