1727P - Distribution of the PAM50 breast cancer subtypes within each pathology-based group: a combined analysis of 15,339 patients across 29 studies

Date 11 September 2017
Event ESMO 2017 Congress
Session Poster display session
Topics Breast Cancer
Pathology/Molecular Biology
Presenter Juan Miguel Cejalvo
Citation Annals of Oncology (2017) 28 (suppl_5): v595-v604. 10.1093/annonc/mdx391
Authors J.M. Cejalvo, T. Pascual, A. Fernández-Martínez, B. Adamo, N. Chic, M. Vidal, L. Rodelo, M. Muñoz, A. Prat
  • Medical Oncology  , Hospital Clinic y Provincial de Barcelona, 8036 - Barcelona/ES

Abstract

Background

Current classification of breast cancer in the clinical setting is based on pathology-based biomarkers such as hormone receptors (HR) and HER2. More recently, identification of the intrinsic molecular subtypes (IS) within each pathology-based group (i.e. HR+/HER2-, HR+/HER2+, HR-/HER2+ and triple-negative [TN]) is revealing clinical value. The objective of this study is to assess the distribution of the IS within each pathology-based group in a large series of breast cancer.

Methods

Twenty-nine studies were identified from the literature (2009–2017) in which IS and pathology-based data were reported. HR was evaluated by immunohistochemistry (IHC) and HER2 by IHC and/or FISH according to standard criteria. Pathology-based groups were divided into 4 groups: HR+/HER2-, HR+/HER2+, HR-/HER2+ and TN. IS (Luminal A [LumA], Luminal B [LumB], HER2-enriched [HER2-E], Basal-like [BL] and Normal-like) were identified using the research-based, or the standardized, PAM50 gene expression-based assay.

Results

PAM50 and pathology data was available in 15,339 patients. The distribution of the PAM50 IS within each IHC-based group is shown in Table 1. Within HR+/HER2- group (n = 9,768), non-luminal subtypes (HER2-E and BL) represented 5.6% and 2.2%, respectively. Within HR+/HER2+ group (n = 1,727), HER2-E and BL represented 29.2% and 2.1%, respectively. Within HR-/HER2+ group (n = 1,332), non-HER2-E subtypes (Luminal A/B and BL) represented 9.3% and 13.8%, respectively. Finally, within TN (n = 2,512), non-BL subtypes (Luminal A/B and HER2-E) represented 5.9% and 11.1%, respectively.Table:

1727P

IHC-BasedPAM50 intrinsic subtype distribution (%)
n = 15,339%LumALumBHER2-EBLNormal
HR+/HER2-63.6854.4734.415.642.243.24
HR+/HER2+11.2634.4530.5729.182.083.71
HR-/HER2+8.686.912.4069.7413.817.13
HR-/HER2-16.383.532.3911.1578.234.70

Conclusions

Our results confirm previous observations that all IS are represented within each pathology-based group. Based on our observations, future clinical trials in unselected breast cancer patient populations should be sufficiently powered to address the prognostic and predictive ability of the IS.

Clinical trial identification

Legal entity responsible for the study

Hospital Clinic Barcelona. August Pi I Sunyer Biomedical Research Institute (IDIBAPS)

Funding

None

Disclosure

All authors have declared no conflicts of interest.