Evaluation of HER-2/neu in Serum and Tissue of Primary and Metastatic Breast Cancer Patients using an Automated Enzyme Immunoassay

Serum HER-2/neu concentrations were evaluated in 172 healthy subjects, 176 primary and 55 metastatic breast cancer patients, employing a new automated assay (Bayer Immuno 1™ serum HER-2/neu). Using 13 ng/mL as the cutoff, abnormal HER-2/neu serum levels were found in 8% (14/176) of primary and 50.9% (28/55) of metastatic breast cancer patients. Both in primary and metastatic breast cancer a significant relationship was found with the stage of the disease when serum HER-2/neu was considered as a categorized variable (p=0.0003 and p=0.02, respectively), but not when it was taken as a continuous variable (p=0.247 and p=0.146, respectively). Moreover, we evaluated the correlation between Immuno 1™ HER-2/neu and Oncogene Research Products ELISA assay in 53 normal subjects, 46 primary and 34 metastatic breast cancer patients. The correlation was relatively good (p<0.0001), although substantial differences could be found in single cases. The Immuno 1™ assay was also evaluated for the first time in breast cancer tissue. The method, which showed good performance both in terms of imprecision and linearity, was used to measure HER-2/neu protein in 140 cytosol samples from primary breast cancer tissue and in homogenates from 40 matched cases. The correlation between the two matrixes was very close (p<0.0001). By contrast, no correlation was found between serum and matched cytosol (p=0.101) or ho-mogenate samples (p=0.511).