Tissue microarray-based studies of patients with lymph node negative breast carcinoma show that met expression is associated with worse outcome but is not correlated with epidermal growth factor family receptors.

BACKGROUND: It has been shown that receptor tyrosine kinases (RTKs) predict outcome in patients with breast carcinoma. Although RTKs are a large family, HER-2, epidermal growth factor receptor (EGFR), Met (hepatocyte growth factor receptor), and others all have shown the ability to predict outcome. However, it remains unclear whether these markers are defining the same subpopulation of patients with breast carcinoma. In this study, the authors attempted to determine the correlation between RTKs on the basis of their ability to stratify a population according to outcome.

METHODS: The authors used tissue microarray technology to study 324 patients with lymph node negative breast carcinoma who had 20-40 years of follow-up. Expression was assessed using immunohistochemical stains for Met, EFGR, fibroblast growth factor receptor (FGFR), and HER-2. Expression levels were assessed by two observers, and correlations were analyzed. Standard pathology information, including tumor size, nuclear grade, Ki-67 receptor status, and estrogen and progesterone receptor expression levels, also was collected.

RESULTS: RTK expression in the study cohort revealed two strong correlations. Specifically, HER-2 and EGFR showed similar expression patterns (P < 0.0001), and Met cytoplasmic domain and FGFR cytoplasmic staining showed similar expression patterns (P < 0.0001), but no correlation was found between the two groups. Of these RTKs, only high levels of Met cytoplasmic domain showed significance as a prognostic marker defining a shortened survival compared with the rest of the population (P = 0.0035; relative risk, 2.04). In the same group of patients, HER-2, hormone receptor status, and other RTK family receptors were not correlated with outcome. In multivariate analysis, only Met cytoplasmic domain and tumor size showed independent predictive value.

CONCLUSIONS: The current results indicate that the cytoplasmic domain of Met shows a unique staining pattern and defines a set of patients unique from the set of patients defined by overexpression of HER-2, EGFR, or hormone receptors. Furthermore, this group of patients is associated tightly and independently with worse outcome.