Serum levels of shed Her2/neu protein in men with prostate cancer correlate with disease progression

Purpose: We determined the association between serum levels of shed Her-2/neu protein and disease progression in men with prostate cancer. Materials and Methods: Serum from 279 patients enrolled in a prospective serum bank and database at New York University Medical Center was analyzed using the Food and Drug Administration approved Immuno-1™ Her-2/neu assay. Patients were classified by the Prostate-Specific Antigen Working Group model into 5 groups, namely group 1-no evidence of cancer in 60, group 2-clinically localized disease in 67, group 3-prostate specific antigen increasing after therapy and no clinical metastases in 77, group 4-clinical metastases and castration sensitivity in 42, and group 5-clinical metastases and castration resistance in 33. A cutoff of 14 ng/ml for normal serum Her-2/neu was established based on the 95th order statistic in group 1. Results: Of 279 patients 37 (13.3%) had increased serum Her-2/neu, that is 5%, 11.9%, 10.4%, 16.7% and 33.3% in groups 1 to 5, respectively. There was a significant difference between patients with (groups 4 and 5) and without (groups 2 and 3) clinical metastases (p = 0.006). In group 5 patients serum Her-2/neu was significantly higher than in group 2 patients (p <0.02). The risk of cause specific death increased significantly with each unit increase in serum Her-2/neu (p <0.001). Conclusions: Increased serum Her-2/neu correlates with the presence of metastatic disease and it may indicate an increased risk of death in patients with castrate, metastatic prostate cancer. The detection of serum Her-2/neu is a minimally invasive alternative to tumor sampling for identifying potential candidates for anti-Her-2/neu treatment strategies. Further studies are needed to optimize this assay for application in the clinical setting.