PURPOSE Epidermal growth factor (EGF) is a ligand for the epidermal growth factor receptor (EGFR). Human epidermal growth factor receptor 2 (HER2) shares common signal pathways and forms a heterodimer with EGFR. In this study, we investigated the clinical and pathologic implications of serum EGF levels in patients with HER2-positive metastatic breast cancer (MBC).

METHODS We analyzed serum EGF levels from baseline serum samples of consecutive patients with HER2-positive MBC who received first-line trastuzumab plus taxane chemotherapy and correlated them with treatment outcomes and pathologic features.

RESULTS A total of 50 women were analyzed. The median age was 47 years (range 27-72 years). Patients with high serum EGF levels (≥10.0 pg/mL) had significantly longer overall survival (47.0 months (95 % confidence interval (CI) 28.3-65.7 months) vs. 23.3 months (95 % CI 13.5-33.1 months); p = 0.009) with a tendency toward longer progression-free survival (p = 0.123). Serum EGF levels were not associated with hematologic or cardiac adverse events. Progesterone receptor-positive patients had significantly higher serum EGF levels than progesterone receptor-negative patients (24.3 pg/mL (range 9.5-69.0 pg/mL) vs. 12.3 pg/mL (range 0.0-59.5 pg/mL); p = 0.006).

CONCLUSIONS Our data suggest that high serum EGF levels may be associated with good prognosis in patients with HER2-positive MBC receiving trastuzumab plus taxane chemotherapy. In addition, serum EGF levels were associated with progesterone receptor positivity.