Elsevier

Annals of Oncology

Volume 23, Issue 12, December 2012, Pages 2997-3006
Annals of Oncology

reviews
Molecular subclasses of breast cancer: how do we define them? The IMPAKT 2012 Working Group Statement

https://doi.org/10.1093/annonc/mds586Get rights and content
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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.

Keywords

breast cancer
Ki-67
molecular classification
molecular subclasses
PAM50

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These recommendations were presented at the IMPAKT 2012 Breast cancer conference in Brussels, Belgium.