Defining a Test for HER-2/neu Evaluation in Breast Cancer in the Diagnostic Setting

Abstract

In breast cancer amplification of the HER-2/neu oncogene and over-expression of the protein product is associated with poor prognosis, predicts response to some chemotherapeutic regimens and is the target for Herceptin treatment. To date there are several methods to assess the amplification/overexpression of HER-2/neu with each having advantages and disadvantages. We have studied amplification and over-expression of HER-2/neu in 250 consecutive cases of breast cancer (220 invasive and 30 in situ carcinomas) presenting to the Department of Pathology at Women's College Campus of Sunnybrook and Women's College Health Sciences Center. Thirty percent of the invasive carcinomas were node positive. HER-2/neu protein overexpression was assessed by immunohistochemistry (IH) using antibody CB11 and amplification of the gene by differential PCR. The percentage of tumor cells showing CB11 staining was determined and the most significant cut off point for positivity was >10% moderate or strong complete membranous staining. The gene was considered amplified if the density score of the product was >2. There was 94% concordance between the two methods (P value .0001). Both methods were positive in 16% of cases and negative in 78% of cases. Discrepant cases were examined by FISH which confirmed the IH results in 9/11 invasive carcinomas. These results show that there is excellent concordance between IH and PCR. However, immunohistochemistry is easier to perform and cheaper than PCR and could be used in routine assessment of HER-2/neu in breast cancer patients.

Analysis of HER-2/neu amplification in endometrial carcinoma by chromogenic in situ hybridization. Correlation with fluorescence in situ hybridization, HER-2/neu, p53 and Ki-67 protein expression, and outcome

“…2,8 Several methods have been proved to be useful for the assessment of HER-2/ neu status. 4,5,7,[10][11][12][13] Nevertheless, considerable confusion exists with regard to the appropriate method and reagent for testing it in routine clinical practice. 7 Furthermore, most of the methods are beyond the scope of the majority of pathology laboratories due to technical, practical, and economical reasons.…”

“…On the contrary, complete absence of protein expression in amplified tumours could be the result of an intrinsic feedback loop that limits the expression, as well as loss of tissue antigenicity. 11,13,23 Low protein levels of HER-2/neu occasionally seen in normal cyclic and post-menopausal endometrium, with no gene amplification, may be the result of transcription activation.…”

“…In several tumour types, and especially in breast carcinoma, amplification of the HER-2/neu oncogene and overexpression of the protein have been also associated with adverse prognostic factors, and outcome, and they predicted the response to some chemotherapeutic regimens. [2][3][4][5]7,8,13 The p53 tumour suppressor gene has been extensively studied in human neoplasia. Alteration of the gene (mutation or/and deletion) or protein accumulation occurs in over 50% of the cases.…”

“…Overall, HER-2/neu amplification and/or overexpression detected by any of the above-mentioned methods have been reported in about one-fourth of breast 3,[11][12][13] and ovarian cancers, 2 prostate, 6 and lung neoplasias, 5 among others. In patients with endometrial carcinoma, a consensus with regard to levels, correlation with clinicopathologic factors, and predictive value of HER-2/neu alterations has not been reached.…”

“…5,7,[10][11][12][13] However, the majority of these methods are recommended as complementary to assess gene status in doubtful cases by immunohistochemistry, and they are only available in some laboratories. 11,[13][14][15] Thus, there is currently a need of new methods for routine clinical practice. Recently, a modification of the FISH technique, the so-called chromogenic in situ hybridization (CISH), has been described by Tanner et al, 16 which enables the detection of HER-2/neu gene copies with the conventional peroxidase reaction.…”