DETERMINATION OF ERBB2 PROTEIN IN BREAST-CANCER TISSUES BY DIFFERENT METHODS - RELATIONSHIPS WITH OTHER BIOLOGICAL PARAMETERS

Four different methods to measure in parallel the erbB2 protein expres sion (p185(neu)) were evaluated in order to: a) compare two enzyme imm unoassays with the immunohistochemical assays (IHC) and western blotti ng (WE) and b) extrapolate eventual relationships between erbB2 and bi ological parameters. Tissue samples from 248 patients with primary bre ast cancer were consecutively assayed. We used two different cut-off l evels for WE, ELISA, and EIA, defined as follows: 1) the highest level of expression of non malignant tissue was chosen as the discriminant threshold between 'low' and 'elevated' samples: 2) the elevated group was further subdivided into two subgroups: 'intermediate' and 'high', according to their median value. According to the first cut-off, the r esults were considered 'elevated' in about 52% of cases with the three biochemical methods, while using the second cut-off the percentage lo wered to about 26%. Considering this cut-off, the concordance rates be tween the paired biochemical methods ranged between: 78.4% (WE vs EIA) , 93% (ELISA vs EIA), and 82.6% (ELISA vs WE). The comparison between biochemical and immunohistochemical methods gave these concordance rat es: 82% (WE vs IHC), 90.5% (ELISA vs IHC), and 85.5% (EIA vs. IHC). Ac cording to the first cut off level, 27.5% of tumor samples showed IHC detectable p185 levels, in agreement with other immunohistochemical st udies. The relationship between high erbB2 and estrogen and progestero ne receptors showed an inverse association. No relationship was found between erbB2 and axillary lymph node positivity or tumor size. In sho rt, the results of the four methods seem generally well correlated; ne vertheless, it appears that different methodological approaches of mea suring p185(neu) are not completely equivalent, and there is a need fo r an authoritative standardization and quality control for clinical ap plications.