HER-2 DNA quantification of paraffin-embedded breast carcinomas with LightCycler real-time PCR in comparison to immunohistochemistry and chromogenic in situ hybridization

Objectives: To compare the detection of HER-2 status by real-time PCR, on paraffin-embedded breast carcinomas, in respect to immunohistochemistry (IHC) and chromogenic in situ hybridization (CISH). Design and methods: Paraffin-embedded breast carcinomas collected from 85 patients diagnosed with early stage breast cancer were analyzed for HER-2 gene amplification by real-time PCR and CISH, as well as for HER-2 protein expression by IHC. Results: HER-2 gene amplification was observed in 19 (22.4%) of 85 breast cancer patients by real-time PCR and in 19 (22.4%) of 85 patients by CISH. Strong (3+) HER-2 protein over-expression was observed in 13 (15.3%) out of 85 patients. Moreover, there were 4 out of 85 (4.7%) patients that had moderate (2+) HER-2 protein over-expression, while 68 out of 85 (80%) patients had no HER-2 protein over-expression by IHC. There were strong concordance rates between real-time PCR and IHC (79/85, 92.9%, p < 0.0001) and real-time PCR and CISH (77/85, 90.6%, p < 0.0001). The concordance rate between the three methods was 90.6% (p < 0.0001). Conclusions: Our data show that the results obtained for amplification of HER-2 by real-time PCR on the LightCycler are comparable to those obtained by IHC and CISH. (c) 2006 The Canadian Society of Clinical Chemists. All rights reserved.