[1039] An early decrease in serum HER-2/neu levels after initiation of primary chemotherapy for HER-2 positive breast cancer indicates response to treatment.

Mazouni C, Hall A, Anderson K, Peintinger F, Fritsche H, Andre F, Yekell S, Arun B, Buzdar AU, Esteva F, Pusztai L, Cristofanilli M.. M.D. Anderson Cancer Center, Houston, TX

Introduction: To determine the utility of detection of the extracellular domain of the Her-2/neu receptor in the serum of patients with primary breast cancer receiving neoadjuvant chemotherapy.
Materials and Methods: Her-2/neu extracellular domain (ECD) was measured in sera obtained from 39 patients with stage II-III primary breast cancer, HER2-amplified undergoing neoadjuvant chemotherapy. Patients were randomly assigned to either four cycles of paclitaxel followed by four cycles of fluorouracil, epirubicin, and cyclophosphamide (FEC) (n=10) or to the same chemotherapy with simultaneous weekly trastuzumab for 24 weeks (n=29). Changes in HER-2/neu were monitored with the Bayers HER-2/neu assay over 6 months (baseline, week 3, 6 and 24) and correlated with pathological response to treatment. The comparisons between serum HER-2/neu baseline and serial throughout treatment concentrations were made with the Wilcoxon-signed ranks test.
Results: The mean serum HER-2/neu baseline concentration was 20.3 ng/mL with a median of 13.6 ng/mL. In 28.2% of patients, elevated concentration of the HER-2/neu ECD (> 15 ng/mL) was detected before initiation of chemotherapy (8.3-232.8ng/mL). There was no correlation between HER-2 FISH amplification and serum HER-2/neu levels (p=0.42). A decrease of the median HER-2/neu levels after week 3 and week 6 of chemotherapy was seen in the group with pathological complete response (p= 0.003), whereas no significant change in HER-2/neu levels was observed in the group with residual disease (p=0.11). A decrease in the median HER-2/neu levels after week 6 of chemotherapy was only seen in the group of patient who received trastuzumab (p=0.007). No significant difference in baseline HER-2/neu ECD levels was observed between the groups who achieved pathological complete response and the group with residual disease (p=0.41).
Conclusion: A decrease in serum Her-2/neu level indicates response to treatment in patients receiving primary chemotherapy and serve to monitor trastuzumab-based regimens.

Thursday, December 14, 2006 5:00 PM

Poster Session I: Prognosis and Response Prediction: Predictive Factors I (5:00 PM-7:00 PM)