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HER-2 Gene Amplification, HER-2 and Epidermal Growth Factor Receptor mRNA and Protein Expression, and Lapatinib Efficacy in Women with Metastatic Breast Cancer

Authors' Affiliations: ¹ Norris Comprehensive Cancer Center, University of Southern California; ² Geffen School of Medicine, University of California at Los Angeles; ³ Response Genetics, Inc., Los Angeles, California; ⁴ National Cancer Research Network Coordinating Centre, University of Leeds, Leeds, United Kingdom; ⁵ Sandro Pitigliani Medical Oncology Unit, Prato, Italy; ⁶ Allegheny General Hospital, Pittsburgh, Pennsylvania; and ⁷ Medicine Development Centre Oncology, GlaxoSmithKline, Collegeville, Pennsylvania

Requests for reprints: Michael F. Press, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Avenue, Suite 5409, Los Angeles, CA 90033-0800. Phone: 323-865-0563; Fax: 323-865-0122; E-mail: press{at}usc.edu.

Purpose: Biomarkers from two randomized phase III trials were analyzed to optimize selection of patients for lapatinib therapy.

Experimental Design: In available breast cancer tissue from EGF30001 (paclitaxel ± lapatinib in HER-2-negative/unknown metastatic breast cancer, n = 579) and EGF100151 (capecitabine ± lapatinib in HER-2-positive metastatic breast cancer, n = 399), HER-2 gene amplification by fluorescence in situ hybridization (FISH), HER-2 mRNA by reverse transcription-PCR (RT-PCR), HER-2 protein expression by HercepTest immunohistochemistry (IHC), epidermal growth factor receptor (EGFR) mRNA level by RT-PCR, and EGFR protein by IHC were analyzed and compared with clinical outcome. HER-2 was determined by FISH in an academic reference/research laboratory and in a large, high-volume commercial reference laboratory.

Results: The HER-2 gene was amplified in 47% (344 of 733) and IHC was 3+ in 35% (279 of 798), with significant correlation (P < 0.01) between FISH and IHC. Positive EGFR immunostaining (IHC 1+, 2+, or 3+) in 28% (213 of 761) correlated with EGFR mRNA levels by RT-PCR (r = 0.59; P < 0.01). HER-2 gene amplification/overexpression was associated with improved clinical outcomes (progression-free survival; P < 0.001) in both trials. A significant improvement in outcome was seen in FISH-positive and IHC 0, 1+, or 2+ patients. HER-2 mRNA expression correlated with HER-2 FISH (r = 0.83) and IHC status (r = 0.72; n = 138). No correlation was found between EGFR expression (IHC or mRNA) and responsiveness to lapatinib regardless of HER-2 status. Although a significant correlation with lapatinib responsiveness was observed among "HER-2-negative" breast cancer patients in the large, high-volume commercial reference laboratory, this was not confirmed in the academic reference/research laboratory.

Conclusions: Women with HER-2-positive metastatic breast cancer benefit from lapatinib, whereas women with HER-2-negative metastatic breast cancer derive no incremental benefit from lapatinib.

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