Serum HER-2 extracellular domain (ECD) before the first metastasis in 128 breast cancer patients

We studied the serum HER-2 extracellular domain (sHER-2) before the first metastases in 128/701 breast cancer patients diagnosed and followed-up in our institution who developed metastases as the first relapse. sHER-2 was measured by an enzyme-linked immnunosorbent assay and CA 15.3 by an immunoradiometric assay. Non-parametric statistics were used. sHER-2 and CA 15.3 before and after primary treatment were measured in a previous part of the study. Before first metastases, 45% of the samples were over 12 microg/l of sHER-2 (cut-off) and were significantly related to sHER-2 values before and after primary treatment (P = 0.0350 and P < 0.0001 respectively). Concordance with CA 15.3 was 56.25 % (weak correlation, rho = 0.263). sHER-2 levels differed according to the sites of the metastases (P = 0.0199), the highest levels were found in liver and lung metastases. A median sHER-2 lead time of 254 days was found for 18/28 (64.3 %) patients before first metastasis. Pre-metastatic sHER-2 levels showed strong univariate (Kaplan-Meier method, P = 0.0014) and multivariate prognostic values (Cox model, P < 0.0001) for survival after first metastasis. In recurrent breast cancer, elevated levels of sHER-2 enabled an early detection of occult metastases and the identification of patients with a high probability of shortened survival.