title: Serum EGFR levels and efficacy of trastuzumab-based therapy in patients with metastatic breast cancer.
abstract: The antibody trastuzumab inhibits signal transduction in Her-2/neu overexpressing human breast cancer. However, the activation of co-expressed EGFR has also been show to additionally modulate the anti-tumoural effects of this drug. Similar to Her-2/neu, the extra cellular binding region of EGFR is believed to be proteolytically released from the cell surface upon receptor activation and can be detected in patients' serum (sEGFR). Considering the biological significance of an interaction between EGFR and Her-2/neu signalling in other human malignancies, we have investigated if trastuzumab treatment would affect sEGFR in 33 patients with Her-2/neu overexpressing metastatic breast cancer. We detected EGFR expression in 33% of Her-2/neu overexpressing breast tumours. In contrast to serum Her-2/neu (ECD) levels, which were correlated with the degree of Her-2/neu expression (P=0.048, Mann-Whitney test), we did not detect significant differences between sEGFR serum levels in EGFR expressing or non-expressing tumours. Furthermore, sEGFR serum levels were not correlated with clinical parameters such as response or clinical benefit rates, and no association was found between increased sEGFR levels and progression-free survival or overall survival. While we have previously observed a selective and significant decrease of ECD levels in patients who derived a clinical benefit from trastuzumab treatment during the first weeks of treatment, we were unable to find similar alterations in sEGFR concentrations. We therefore conclude that the measurement of systemic sEGFR levels in addition to ECD serum concentrations do not allow the prediction of clinical course of trastuzumab-treated patients more accurately.
authors.affiliation: Ludwig Boltzmann Institute for Clinical and Experimental Oncology, Vienna, Austria.
authors.forename: Gernot
authors.initials: G
authors.lastname: Hudelist
authors.forename: Wolfgang J
authors.initials: WJ
authors.lastname: Köstler
authors.forename: Daphne
authors.initials: D
authors.lastname: Gschwantler-Kaulich
authors.forename: Klaus
authors.initials: K
authors.lastname: Czerwenka
authors.forename: Ernst
authors.initials: E
authors.lastname: Kubista
authors.forename: Ruth
authors.initials: R
authors.lastname: Müller
authors.forename: Samir
authors.initials: S
authors.lastname: Helmy
authors.forename: Mahmood
authors.initials: M
authors.lastname: Manavi
authors.forename: Christoph C
authors.initials: CC
authors.lastname: Zielinski
authors.forename: Christian F
authors.initials: CF
authors.lastname: Singer
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D009362:Neoplasm Metastasis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D018709:Statistics, Nonparametric; D000068878:Trastuzumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab