title: Immunohistochemical assay for epidermal growth factor receptor on paraffin-embedded sections: validation against ligand-binding assay and clinical relevance in breast cancer.
abstract: Epidermal growth factor receptor (EGFR) has been the subject of much research since it was first described as a prognostic factor in breast cancer. The assay methods used and results obtained vary widely between studies. In this study 88 primary breast cancers were assayed for EGFR using a novel immunohistochemical assay performed on paraffin-embedded sections. The monoclonal antibody used was raised against purified, denatured EGFR, reacts with an epitope on the external domain and does not interfere with ligand binding. Twenty-two per cent of the tumours were EGFR positive using this assay. The results obtained were significantly correlated with those obtained by ligand-binding assay (r = 0.621, P = 0.011). The concordance rate was 82% (P < 0.001). The majority of discordant results could be explained by the presence of benign breast tissue and other non-malignant elements which could be seen to express EGFR on the immunohistochemical assay and were excluded from the score for this, but would be incorporated into ligand-binding assay results. The well-established inverse relationship between EGFR (as measured by this assay) and oestrogen receptor (ER) was seen (chi 2 = 24.9, P < 0.0001). In addition, in this exploratory study on a limited tumour set, EGFR was a significant adverse prognostic factor (on univariate but not multivariate analysis) for both relapse-free survival (P = 0.02) and overall survival (P = 0.03) when measured by this immunohistochemical assay, but was not significant when measured by ligand-binding assay.
authors.affiliation: Department of Academic Biochemistry, Royal Marsden Hospital, London, UK.
authors.forename: J C
authors.initials: JC
authors.lastname: Newby
authors.forename: R P
authors.initials: RP
authors.lastname: A'Hern
authors.forename: R D
authors.initials: RD
authors.lastname: Leek
authors.forename: I E
authors.initials: IE
authors.lastname: Smith
authors.forename: A L
authors.initials: AL
authors.lastname: Harris
authors.forename: M
authors.initials: M
authors.lastname: Dowsett
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001940:Breast / Q000166:cytology / Q000473:pathology; D001943:Breast Neoplasms / Q000737:chemistry / Q000401:mortality / Q000473:pathology*; D004847:Epithelial Cells; D004848:Epithelium / Q000473:pathology; D066246:ErbB Receptors / Q000032:analysis*; D005260:Female; D005500:Follow-Up Studies; D006652:Histological Techniques; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008207:Lymphatic Metastasis; D008875:Middle Aged; D010232:Paraffin; D011237:Predictive Value of Tests; D011379:Prognosis; D011869:Radioligand Assay; D015203:Reproducibility of Results; D016019:Survival Analysis; D013997:Time Factors
chemical_list: D010232:Paraffin; D066246:ErbB Receptors