Abstract P3-08-07: HER2 positive breast carcinomas: trend in evolution between 1998 and 2008 and relationship with clinico-pathological characteristics in a population based study.

Abstract

Background: Determination of HER2 status in invasive breast carcinomas is now mandatory for the optimal treatment of the patient. A vast majority of initial published studies described positivity in about 20 to 25 % of breast carcinomas, but the proportion of HER2 positive gene expression in women with breast cancer varies in the literature from 9 to 74%. The population of the tumor analyzed (for example histologic types, stage, age), the type of the assays used and the lack of uniformity or quality controls in detection assays may partly explain these differences. Our study describes the evolution of HER2 positive invasive breast cancer proportions during a period of 10 years and identifies clinical and pathological characteristics of these positive tumors. Methods: Based on the regional, population-based breast cancer registry, we identify 2396 patients diagnosed with invasive breast cancer in the Côte-d'Or department and treated in a single institution between 1998 and 2008. The HER2 status was determined by immunohistochemistry and by fluorescence in situ hybridization by a single team that performed regular internal quality controls and participated to multiannual external international quality control programs. Results: During the 1998–2008 period, 12.8% of invasive breast cancers were identified as HER2 positive, with no trend to annual variations (p = 0.27). During the same period, despite an increase of 45% of the annual diagnosed cancers in the institution, the clinical and pathological characteristics such as age, tumor size, grade, hormonal receptors expression remain stable. We only noticed a slight but significant increase of lobular carcinomas (p = 0.036). In multivariate analysis, HER2 positivity was as expected associated with: hormonal receptor negative status (OR = 1.7 [IC95%: 1.2–2.4], p = 0.0035), metastatic presentation at diagnosis (OR = 2 [IC95%: 1.2–3.4], p = 0.0092), ductal subtype (OR = 1.9 [IC95%: 1.1–3.1], p = 0.0178) and high SRB grade (OR = 2.8 [IC95%: 1.7–4.5] for SBR II, OR = 5.4 [IC95%: 3.2–9.1] for SBR III, p = 0.0035). Conversely, patients older than 75 years presented mostly HER2 negative tumors (OR = 0.5 [IC95%: 0.3–0.8], p < 0.0001). Conclusions: This population based study on HER2 breast cancer status emphasizes that in a population with stable clinical and tumoral characteristics, when standardized and controlled assays are used, the proportion of HER positive tumors remains stable over a large period and is lower than usually reported (12.8%). Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-08-07.