Abstract
BACKGROUND.
Epidermal growth factor receptor (EGFR, HERβ1, and __erbB__1) is overexpressed in primary breast cancer and had been identified as a poor prognostic factor.
METHODS.
Pretreatment serum EGFR levels were quantified by using an enzymeβlinked immunoadsorbent assay in a Phase III firstβline trial of letrozole and tamoxifen and were correlated with patient outcomes.
RESULTS.
Serum EGFR levels in a control group of 117 healthy, postmenopausal women measured 64.1 Β± 13.3 ng/mL (mean Β± standard deviation). Using a cutoff EGFR level of 44.1 ng/mL from the control group (5% nonparametric method), 53 of 535 patients (10%) had decreased serum levels of EGFR. Patients with decreased serum EGFR had no significant difference in objective response rate (ORR), clinical benefit rate (CBR), time to progression (TTP), or time to treatment failure (TTF); however, they did have significantly reduced survival compared with patients who had normal serum EGFR levels (median survival, 23.3 months vs. 30.9 months; P = .007). A combined analysis of pretreatment serum EGFR and HERβ2 yielded no additional predictive information for ORR, CBR, TTP, or TTF compared to serum HERβ2 alone. However, in the current analysis, a subgroup of patients who had decreased serum EGFR and normal serum HERβ2 was identified (n = 39 of 535 patients; 7.3%) that had significantly reduced survival compared with patients who had normal serum levels of both EGFR and HERβ2 (median survival, 23.5 months vs. 37.1 months; P = .005). In multivariate analysis, a decreased serum EGFR level remained a significant independent prognostic factor for decreased survival (hazards ratio, 1.58; P = .007).
CONCLUSIONS.
In patients who had metastatic breast cancer, decreased serum EGFR/normal serum HERβ2 predicted shorter survival compared with patients who had normal levels of serum EGFR/HERβ2. This patient subgroup deserves further study to assess their response to and selection for antiβEGFRβdirected therapies. Cancer 2006. Β© 2006 American Cancer Society.