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Breast Carcinomas arising at a Young Age: A Unique Biology or a Surrogate for Aggressive Intrinsic Subtypes

ABSTRACT: Breast cancer is no longer viewed as a homogenous disease, but rather a compilation of several distinct subtypes as defined by microarray or other large scale genomic analyses. Based on prior reports, we hypothesized that younger women’s breast tumors would be enriched for more aggressive subtypes (i.e. Basal-like) and higher grade, and that age-specific gene expression differences may be highly dependent on subtype classification and/or grade. Using two independent datasets, our current analysis shows that breast tumors arising in women aged = 45 years are enriched for the Basal-like subtype (and higher grade) while those aged = 65 years are enriched for Luminal tumors. Moreover, when evaluating gene expression differences between age-defined groups, sizable gene lists were identified which diminished to few, if any, age-specific genes when statistically correcting for significant clinical factors (i.e. subtype, grade, etc). Keywords: reference x sample 344 breast tumor samples hybridized with Stratagene common reference and profiled on Agilent microarrays.

ORGANISM(S): Homo sapiens

SUBMITTER: Anders CK

PROVIDER: S-ECPF-GEOD-20624 | biostudies-other | 2011 Jan

REPOSITORIES: biostudies-other

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Project description:IntroductionThe St Gallen International Expert Consensus on the Primary Therapy of Early Breast Cancer 2013 recognized substantial progress in the pathological characterization of breast cancer subtypes. A useful surrogate definition was developed to distinguish luminal A-like breast cancer from luminal B-like disease based on a combination of estrogen receptor (ER), progesterone receptor (PgR) and Ki-67 status, without a requirement for molecular diagnostics. Differences depend upon the choice of the threshold value for Ki-67 and the requirement for substantial PgR positivity. We aimed to verify the suitability of the new surrogate definitions of luminal subtypes in terms of distant disease control in a large series of patients.MethodsWe studied 9,415 women with a median follow-up of 8.1 years who (1) had ER-positive, human epidermal growth factor receptor 2 (HER2)-negative early breast cancer and (2) had undergone surgery at the European Institute of Oncology between 1994 and 2006. We evaluated distant disease-free survival of patients with "low" (<14%), "intermediate" (14% to 19%) or "high" (?20%) Ki-67 positivity stratified by PgR expression (negative or low versus high). We calculated the cumulative incidence of distant events, considered competing events and performed multivariable analysis adjusted for pathologic tumor stage, pathologic node stage, tumor grade, peritumoral vascular invasion and menopausal status.ResultsLack of substantial PgR positivity was associated with poorer outcomes only for patients with an intermediate Ki-67 level (P<0.001). The 4,890 patients (51.9%) with low Ki-67 level (any PgR expression level) or with intermediate Ki-67 level but substantial PgR positivity had comparably good outcomes and thus may represent a most advantageous grouping of those with luminal A-like disease.ConclusionsThe updated pathological definition of intrinsic molecular subtypes may maximize the number of patients classified as having the luminal A-like intrinsic subtype of breast cancer and for whom the use of cytotoxic drugs could mostly be avoided.

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Breast Carcinomas arising at a Young Age: A Unique Biology or a Surrogate for Aggressive Intrinsic Subtypes

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