title: Molecular subclasses of breast cancer: how do we define them? The IMPAKT 2012 Working Group Statement.
abstract: The 2012 IMPAKT task force investigated the medical usefulness of current methods for the classification of breast cancer into the 'intrinsic' molecular subtypes (luminal A, luminal B, basal-like and HER2). A panel of breast cancer and/or gene expression profiling experts evaluated the analytical validity, clinical validity and clinical utility of two approaches for molecular subtyping of breast cancer: the prediction analysis of microarray (PAM)50 assay and an immuno-histochemical (IHC) surrogate panel including oestrogen receptor (ER), HER2 and Ki67. The panel found the currently available evidence on the analytical validity and clinical utility of Ki67 based on a 14% cut-off and PAM50 to be inadequate. The majority of the working group members found the available evidence on the analytical validity, clinical validity and clinical utility of ER/HER2 to be convincing. The panel concluded that breast cancer classification into molecular subtypes based on the IHC assessment of ER, HER2 and Ki67 with a 14% cut-off and on the PAM50 test does not provide sufficiently robust information to modify systemic treatment decisions, and recommended the use IHC for ER and HER2 for the identification of clinically relevant subtypes of breast cancers. Methods for breast cancer classification into molecular subtypes should, however, be incorporated into clinical trial design.
authors.affiliation: Department of Medical Oncology, Georges-François Leclerc Cancer Center, Dijon, France.
authors.forename: S
authors.initials: S
authors.lastname: Guiu
authors.affiliation: Department of Biostatistics and Epidemiology, Jules Bordet Institute, Brussels, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Michiels
authors.affiliation: Department of Medical Oncology, Gustave Roussy Institute, Villejuif, France. Electronic address: fandre@igr.fr.
authors.forename: F
authors.initials: F
authors.lastname: André
authors.affiliation: Department of Oncology, Vall d'Hebron Institute of Oncology, Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Cortes
authors.affiliation: Institute of Pathology, Charité University Medicine, Berlin, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Denkert
authors.affiliation: Medical Oncology Unit, Hospital of Prato, Istituto Toscani Tumori, Prato, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Di Leo
authors.affiliation: Department of Medical Oncology, Beaumont Hospital, Dublin, Ireland.
authors.forename: B T
authors.initials: BT
authors.lastname: Hennessy
authors.affiliation: Department of Genetics, Institute for Cancer Research, Oslo University Hospital, Norwegian Radium Hospital, Oslo, Norway.
authors.forename: T
authors.initials: T
authors.lastname: Sorlie
authors.affiliation: Centre des Tumeurs, Jules Bordet Institute, Brussels, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Sotiriou
authors.affiliation: Institute of Cancer Research, Royal Marsden Foundation Trust, London, UK.
authors.forename: N
authors.initials: N
authors.lastname: Turner
authors.affiliation: Department of Pathology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Van de Vijver
authors.affiliation: European Institute of Oncology, University of Milan, Milan, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Viale
authors.affiliation: Department of Translational Research, Jules Bordet Institute, Brussels, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Loi
authors.affiliation: Breakthrough Breast Cancer Research, Institute of Cancer Research, London, UK.
authors.forename: J S
authors.initials: JS
authors.lastname: Reis-Filho
mesh_terms: D001943:Breast Neoplasms / Q000145:classification* / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D019394:Ki-67 Antigen / Q000235:genetics; D046228:Microarray Analysis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics; D011960:Receptors, Estrogen / Q000235:genetics
chemical_list: D019394:Ki-67 Antigen; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; C508053:ERBB2 protein, human