[1005] Serial measurement of serum extracellular domain of HER2 (ECD/HER2) has prognostic value in metastatic breast cancer.

Bramwell VHC, Doig GS, Tuck AB, Wilson SM, Tonkin KS, Tomiak A, Perera F, Vandenberg TA, Chambers AF.. London Regional Cancer Program, London, ON, Canada; Tom Baker Cancer Centre, Calgary, AB, Canada; University of Sydney, Sydney, Australia

Background: In a prospective study of 158 women with metastatic breast cancer, our group has shown that serial measurement in plasma of osteopontin (OPN), a novel tumor marker, is strongly associated with poor survival (Bramwell V et al, Clin Cancer Res 2006, 12:3337). As several studies have suggested that serial measurement of serum ECD/HER2 also has prognostic value in metastatic breast cancer, we present data on this marker analysed in the same patient population.
Materials and Methods: Blood samples were taken at every clinic visit from the time of diagnosis of metastases until death, for 158 women with advanced breast cancer. Serum ECD/HER2 was measured using a commercially available kit. Multivariate time-dependent survival analyses were conducted using models that right censored patient outcomes 3, 6 and 12 months after last ECD/HER2 measurement.
Results: ECD/HER2 was measured in 1378 samples (median, 9 per patient). Baseline data for ECD/HER2 were available on 137 women. Median level was 10.2 ng/ml (range 4.1 40.4), with 34 (25%) patients having elevated levels (upper limit of normal 15 ng/ml). Higher baseline levels of ECD/HER2 were correlated with poor survival (p = 0.001). Data on serial measurements of ECD/HER2 after baseline were available for 156 women, and any subsequent increases were associated with worse survival at 3, 6 and 12 mos after the last measurement (p = 0.025, RR 1.57, at 12 mos). Exploratory regression models examining ECD/HER2 increases of 3, 5, 12, 15 ng/ml showed that ECD/HER2 increases of 12 ng/ml had the strongest association with survival (p = 0.0001, RR 5.89, at 12 mos).
Conclusions: Serial measurement of both OPN and ECD/HER2 have prognostic value for survival in this cohort of women with metastatic breast cancer. We are further exploring their relative value in monitoring survival and response to treatment.

Thursday, December 14, 2006 5:00 PM

Poster Session I: Detection and Diagnosis: Circulating Markers (5:00 PM-7:00 PM)