EPIDERMAL GROWTH-FACTOR RECEPTORS IN BREAST-CANCER - COMPARISON OF RADIOLIGAND AND IMMUNOCYTOCHEMICAL ASSAYS

Epidermal growth factor receptors (EGFR) are part of second generation biological factors that clinicians caring for breast cancer patients wish to evaluate for their prognostic value. This aim requires the sta ndardization of methods: the radioligand assay (RLA) for the quantific ation of EGF binding sites was performed on membrane pellets from 261 breast cancel samples (ligand binding and hydroxylapatite separation a s recommended by the EORTC Receptor Study Group)l the immunocytochemic al assay (ICA) for the staining of EGFR antigenic sites was performed on fine needle aspiration (FNA) cytology or touch imprints from 97 sur gical specimens. The percentage of EGFR positivity by RLA (specific bi nding higher than 1% of total radioactivity) and the EGFR positive rat e by ICA (more than 5% of stained cells) were respectively 43% and 38% . For 61 cases assayed on the same patient both methods revealed a con cordance of 85%. Our results show that both methods are complementary and give quantitative data and information on tumor heterogeneity when they are performed in parallel. The next step of this study will be t o determine the prognostic value of EGFR in these subpopulations of tu mors for the adjustment of adjuvant treatment.