Background: This prospective pilot study was performed to elucidate whether early changes in serum levels of the Her-2/neu extracellular domain (ECD) reflect histopathological response to trastuzumab-based neoadjuvant therapy in patients with Her-2/neu-overexpressing breast cancer.
Patients and methods: ECD levels were measured throughout neoadjuvant trastuzumab-based treatment in 16 patients using a Her-2/neu Microtiter ELISA.
Results: In 9 (56%) patients with Her-2/neu shedding tumors (ECD > 15 ng/ml), ECD values (in % of baseline) of non-responders vs. responders were 117% vs. 55% on day 8 (p=0.014), 157% vs. 58% on day 22 (p=0.061) and 114% vs. 46% at restaging (p=0.049).
Conclusion: Serial monitoring of serum Her-2/neu ECD levels may represent a valuable tool to predict pathological response to trastuzumab-based neoadjuvant therapy in patients with Her-2/neu-overexpressing tumors.