11007 Background: The HER-2/neu oncoprotein is a transmembrane tyrosine kinase that belongs to the family of epidermal growth factor receptors. It is known to be overexpressed in 20–40% of breast cancers. Increased serum HER-2/neu (sHER-2/neu) concentrations at the beginning of adjuvant breast cancer therapy have been shown to be of prognostic importance (Mehta et al, 1998). Using the sera from the Takeda® Adjuvant Breast Cancer Study with Leuprorelin (TABLE study), we tested for the prognostic value of sHER-2/neu. Methods: A total of 133 premenopausal, node-positive, hormone-receptor positive patients received either 11.25 mg of leuprorelin s.c. every 3 months over 2 years or CMF chemotherapy for 6 cycles. Blood samples were collected at baseline and at 3, 6, 12, 18, 24 and 30 mo. The primary endpoint of the study was to determine the relapse-free survival (RFS) after 2 years. sHER-2/neu was measured using a standardized ELISA (upper limit of normal 15 ng/ml). As the baseline sHER-2/neu concentrations ranged from 3.8–14.0 ng/ml, results were grouped in terciles. Data were analyzed using Kaplan-Meier and Cox Proportional Hazards survival analysis. Results: Material was available from 80 patients in leuprorelin arm and 53 patients in CMF arm. 65 of 133 patients had relapsed during the follow-up time of up 7 years after treatment. The median RFS was 62.9 mo. The RFS time depended on the concentrations of sHER-2/neu at baseline: RFS was significantly shorter in patients of the third tercile with sHER-2/neu levels >8.8 ng/ml than in patients of the first tercile with levels <7.2 ng/ml (p=0.0232). Five years after initial therapy, we found that 73% of patients in the first tercile group of baseline sHER-2/neu had no relapse. In the second tercile, 63.3% of patients were relapse-free, while in the third tercile only 47.2% of patients had not suffered from a relapse. Conclusions: Higher sHER-2/neu concentrations at the beginning of adjuvant therapy in the TABLE-Study have a prognostic importance for RFS. This observation was evaluated irrespective of the HER-2/neu tissue status and could be of clinically importance for adjuvant therapy with the monoclonal anti-HER-2/neu antibody trastuzumab or other anti-HER-2/neu targeted therapies. No significant financial relationships to disclose.