Most TNBCs expressing EGFR are non-specialized invasive ductal carcinomas, whereas others are likely to be rare specialized carcinomas, such as typical medullary carcinoma, apocrine carcinoma, metaplastic carcinoma, and adenoid cystic carcinoma.
Vandetanib (ZD6474, Caprelsa, AstraZeneca), an oral small-molecule tyrosine kinase inhibitor (TKI) that targets the rearranged during transfection receptor (RET), VEGF receptor (VEGFR2-3), and EGF receptor (EGFR), is the first systemic therapy approved by the U.S. Food and Drug Administration (FDA) for the treatment of symptomatic or progressive advanced medullary thyroid cancer (MTC).
Recently, vandetanib (ZD6474), an inhibitor of vascular endothelial growth factor receptor (VEGFR) 2 and VEGFR 3, RET, and epidermal growth factor receptor (EGFR), was approved for the treatment of adults with symptomatic or progressive MTC.
This open-label, phase II study assessed the efficacy of vandetanib, a selective oral inhibitor of RET, vascular endothelial growth factor receptor, and epidermal growth factor receptor signaling, in patients with advanced hereditary MTC.
EGFR tyrosine kinase domain mutations were not a feature of MTCs; however, EGFR polysomy and a strong EGFR expression were detected in 15 and 13% of the tumors respectively.
Several genes relevant to breast cancer metastasis to bone (osteopontin, CTGF, parathyroid hormone receptor, EGFR) were significantly overexpressed in MTCs as compared to DTCs.
The prominent co-expression of c-Myc, TGF-alpha and EGFR proteins indicates that in MTC these factors might be of importance for tumour cell proliferation via autocrine growth stimulation.