Journal of Clinical Oncology, 2008 ASCO Annual Meeting Proceedings (Post-Meeting Edition).
Vol 26, No 15S (May 20 Supplement), 2008: 510
© 2008 American Society of Clinical Oncology

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Abstract

Breast cancer molecular subtypes and locoregional recurrence

University of British Columbia, Vancouver, BC, Canada; British Columbia Cancer Agency, Vancouver, BC, Canada; Washington University School of Medicine, St. Louis, MO; University of Utah Health Sciences Center, Salt Lake City, UT; University of North Carolina at Chapel Hill, Chapel Hill, NC

510

Background: Gene expression profiling studies have consistently revealed prognostically significant breast cancer subtypes: Luminal A (LumA), Luminal B (LumB), HER2, and Basal-like. This study compares the local and regional recurrence rates within these subtypes. Methods: Tissue microarrays were constructed using 4,046 invasive breast cancers referred to the British Columbia Cancer Agency from 1986 to 1992. Breast cancer subtypes were defined using an immunopanel of ER, progesterone receptor (PR), HER2, epidermal growth factor receptor (EGFR), cytokeratin 5/6 and Ki67. Univariate local and regional relapse risks were estimated using Kaplan-Meier survival curves. For multivariate analysis, stratified Cox models were built to determine the hazard ratios of breast cancer subtypes, adjusting for tumor size, grade, lymphovascular invasion, margin status, nodal involvement and age as covariates, and, for local treatments (lumpectomy + radiation, mastectomy, mastectomy + radiation) as strata. Results: 3,038 breast tumors are classifiable into molecular subtypes. 1,324 (44%) patients had lumpectomy + radiation, 494 (16%) had mastectomy + radiation and 1,220 (40%) had mastectomy alone. Defining ER/PR positive, HER2 negative and Ki67<10% as LumA identifies a low risk subtype. HER2+ (ER/PR negative and HER2 positive), and basal-like (ER/PR/HER2 negative but either EGFR or ck5/6 positive) are associated with increased local and regional relapses confirming the aggressive nature of these two subtypes. Lum/HER2+ (ER/PR positive and HER2 positive) and LumB (ER/PR positive, HER2 negative, Ki6710%) subtypes shows significantly worse prognosis in regional but not in local relapse when compared to LumA. Conclusions: Breast cancer subtyping provides additional prognostic information and identifies subgroups with distinct local and regional recurrence risks. Newer targeted systemic treatments may modify this.

Abstract presentation from the 2008 ASCO Annual Meeting