Longitudinal changes in serum HER-2/neu oncoprotein levels in trastuzumab-treated metastatic breast cancer patients.

Background: To evaluate longitudinal variations of serum HER-2/neu extracellular domain (sHER-2) in metastatic breast cancer patients receiving combined trastuzumab treatment.

Patients And Methods: Thirty-three patients were monitored by serial sHER-2 ELISA (Oncogene Science). Results were compared to time to progression (TTP) and survival from treatment initiation. Non parametric statistical tests were used.

Results: Median sHER-2 before first injection was 41.37 ng/ml (range 7.54-1597.00 ng/ml, n=32). Mean sHER-2 levels differed significantly between responders (n=20) and non responders (n=13) (p<0.0001). Median TTP (266 days, range 35-1000 days) was unrelated to clinico-biological variables at diagnosis or number and site of metastases before treatment. Patients with pre-treatment sHER-2 levels < or = 30 ng/ml (n=14) had a significantly longer TTP than the group with sHER-2 > 30 ng/ml (n=18) (p=0.0346) and sHER-2 levels were of prognostic value for overall survival from first injection (p=0.0150).

Conclusion: Our results show that monitoring serum HER-2/neu levels during metastatic breast cancer can provide a real time assessment of a woman's HER-2/neu status and can provide important information for therapeutic decisions.