Proficiency testing of immunohistochemical biomarker assays in breast cancer.

Steroid hormone receptor expression and HER2 status have become an integral part of histopathologic characterization of breast cancer and corresponding biomarker assays have gained important prognostic and predictive impact. Because testing inaccuracy could provide a major hazard to modern breast cancer therapy, a laboratory proficiency testing program has been implemented in Germany using tissue microarrays (TMAs). In four consecutive annual trials with 142 laboratories participating on average per trial, estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (Her2) were determined immunohistochemically by participating laboratories followed by central review of all immunostains. Performance strongly depended on the ambiguity of expression of the target molecule in the test samples. In clearly positive (Allred score 7-8; Her2 3+) or negative tissue samples, the majority of participants (86%) achieved concordance rates exceeding 85%. By contrast, low expression of ER or PR (Allred score 3-4) as well as Her2 status 2+ led to considerable lower concordance rates ranging from 41% (Her2 2+) to 75% (PR). Poor reproducibility was predominantly due to inadequate laboratory performance whereas interobserver agreement (weighted kappa statistics) usually was high (>0.81). Laboratories that participated in more than one of the four subsequent trials (n = 110) showed a highly significant improvement of performance. In conclusion, a TMA-based proficiency testing of biomarkers in breast cancer has been implemented in Germany over a 5-year period and revealed reliable assessment of unambiguously positive and negative test samples. Low-expressing tumor samples with regard to steroid hormone receptor expression and Her2 status 2+ led to inaccurate evaluations by up to 59% of participants. Regularly participating laboratories showed a significant improvement of performance.

Brachyury expression predicts poor prognosis at early stages of colorectal cancer.

Although survival rates of colon cancer patients diagnosed at an early stage (T1-2N0M0; Dukes A) vary considerably according to the studies cited, several studies indicate development of distant metastases already occurring in a considerable percentage of these patients leading to the death of the patients. This particular high risk group cannot be identified properly as no marker exists to identify these patients. As the Wnt/Win pathway plays a crucial role in metastasis formation in colorectal carcinoma, we analysed whether the transcription factor brachyury critically involved in this pathway may predict metastasis formation in these patients. The expression of brachyury-homologous (T) was immunohistochemically analysed in 748 patients and the data were correlated with classical and newer prognostic markers in colorectal cancer. Early stages colorectal cancer patients (T1-2N0M0, Dukes A) showed a significantly decreased survival when brachyury was expressed in the tumour tissue while no correlation was observed in later tumour stages. Hence a subset of colorectal cancers exists in which the ability to metastasise is already present at early stages of tumour growth and this high risk group can now be detected by immunohistochemistry.