[Serum HER-2 determination using a centauer HER-2/neu kit (CLIA method) in metastatic breast cancer]

Employing CLIA and EIA methods simultaneously, we determined serum HER-2/neu levels a total of 92 times in 51 patients with metastatic breast cancer(MBC)and 3 patients with non-recurrent breast cancer, and compared the levels measured by both methods with the level of IHC-staining for HER-2 and the clinical course. Among 20 patients with IHC HER-2/3+ MBC (including FISH+MBC), 14(70%)showed high levels by the CLIA method (>cut-off value of 15.2 ng/mL), whereas only 4(20%)revealed high levels by the EIA method(>cut-off value of 6.5 ng/mL). None of the patients with CR or non-recurrent breast cancer exhibited high levels by either method. Some IHC HER-2(-) patients also frequently showed high levels by the CLIA method. The EIA method not only revealed low-level sensitivity, but also was subject to interference(abnormally low levels)due to trastuzumab administration. The results obtained by the CLIA method were in agreement with the clinical course. In 93 MBC patients(except CR patients)whose serum HER-2 levels were determined by the CLIA method, the initial HER-2 levels were compared with the CEA and CA15-3 levels. Of the 32 IHC HER-2/3+ patients, 25, 13, and 12 were noted to have high serum levels of HER-2, CEA, and CA15-3, respectively. These results indicate that the serum HER-2 level as assessed by the CLIA method is the most sensitive marker of HER-2-positive MBC.