Serum-transforming growth factor-{alpha} (TGF-{alpha}) and response to lapatinib plus capecitabine in HER2-positive (HER2+) metastatic breast cancer (MBC).

1102 Background: Although lapatinib plus capecitabine is effective in trastuzumab-resistant HER2+ MBC, predictive biomarker of the treatment has not been identified. We investigated biomarkers from serum of patients receiving lapatinib and capecitabine. Methods: Patients received lapatinib 1,250 mg once daily and capecitabine 2,000 mg/m2/day, day 1 to 14, every 3 weeks. Serum samples were obtained prior to treatment initiation. Levels of TGF-α, EGF, EGFR-extracellular domain (ECD) and HER2-ECD were measured by ELISA. We analyzed the association between the serum levels and response to the treatment. Besides, the effect of TGF-α on in vitro sensitivity of SK-BR-3 cells to lapatinib was investigated. Results: A total of 64 women were enrolled. All patients had HER2+ MBC and had progressed after trastuzumab containing regimen. The overall response rate was 31.3% and median TTP was 4.5 months in the study population. Among the serum markers, serum TGF-α level was significantly lower in responders (PR) compare...