A multicentre validation of Metasin: a molecular assay for the intraoperative assessment of sentinel lymph nodes from breast cancer patients.

AIMS: Treatment strategies for breast cancer continue to evolve. No uniformity exists in the UK for the management of node-positive breast cancer patients. Most centres continue to use conventional histopathology of sampled sentinel lymph nodes (SLNs), which requires delayed axillary clearance in up to 25% of patients. Some use touch imprint cytology or frozen section for intraoperative testing, although both have inherent sensitivity issues. An intraoperative molecular diagnostic approach helps to overcome some of these limitations. The aim of this study was to assess the clinical effectiveness of Metasin, a molecular method for the intraoperative evaluation of SLNs. METHODS AND RESULTS: RNA from 3296 lymph nodes from 1836 patients undergoing SLN assessment was analysed with Metasin. Alternate slices of tissue were examined in parallel by histology. Cases deemed to be discordant were analysed by protein gel electrophoresis. There was concordance between Metasin and histology in 94.1% of cases, with a sensitivity of 92% [95% confidence interval (CI) 88-94%] and a specificity of 97% (95% CI 95-97%). Positive and negative predictive values were 88% and 98%, respectively. Over half of the discordant cases (4.4%) were ascribed to tissue allocation bias (TAB). CONCLUSIONS: Clinical validation of the Metasin assay suggests that it is sufficiently sensitive and specific to make it fit for purpose in the intraoperative setting.

The use of cell line standards to reduce HER-2/neu assay variation in multiple European cancer centers and the potential of automated image analysis to provide for more accurate cut points for predicting clinical response to trastuzumab.

Immunohistochemical analysis, the most efficient way of assaying for HER-2/neu overexpression in patients with invasive breast cancer, is subject to variation in sensitivity and evaluation when used in multiple laboratories. Cell lines with differing but constant levels of HER-2/neu expression have been advocated as standard material against which assay sensitivity can be gauged. Automated image analysis could provide more precise linear measurements of HER-2/neu expression than the subjective and categorical scoring system originally designed for the HER-2/neu clinical trials. Multiple European laboratories (range, 92-126) stained 7 cell line standards on 6 successive occasions using a variety of immunohistochemical assays for HER-2/neu. During the 2-year study period, a trend toward a standard sensitivity level was observed, with significant improvement in numbers of laboratories achieving appropriate results. Image analysis gave reproducible and significantly different linear values for a total of 621 HER-2/neu results on cell lines previously categorized manually as 3+, 2+, 1+, or 0. The use of cell line standards and image analysis have the potential to assist in standardizing immunohistochemical results for predictive markers and provide more accurate and quantifiable cut points for predicting clinical response to therapy, respectively.