EGFR pharmDx™

DakoCytomation’s FDA-approved IHC assay, validated at AmeriPath in accordance with CLIA and CAP guidelines, is an aid in identifying colorectal cancer patients for treatment with Erbitux™.

Clinical Utility | Specimen Requirements | Methodology | Quality Assurance | Interpretation | Analytic Time | CPT Code | Background | More Information

Clinical Utility

	Metastatic colorectal carcinoma showing moderate membranous staining for EGFR

The EGFR pharmDx™ assay is a qualitative immunohistochemistry (IHC) kit system used to identify Epidermal Growth Factor Receptor expression in normal and neoplastic tissues. The assay specifically detects the EGFR (HER1) protein in EGFR-expressing cells. Patients enrolled in the cetuximab clinical studies were required to have immunohistochemical evidence of positive EGFR expression using the DakoCytomation EGFR pharmDx test.

EGFR pharmDx™ is FDA approved as an aid in identifying colorectal cancer patients eligible for treatment with Erbitux™.

Specimen Requirements

• Paraffin block and one original H & E. Do not recut the block for H & E.
• Indicate on the requisition the type of fixative used. Tissue specimens may be fixed in 10 % neutral buffered formalin, 10% unbuffered formalin, 25% unbuffered formalin, AFA (acetic formalin alcohol), Richard Allen Scientific’s Pen-fix or Bouin’s. Anatech’s PreFer fixative is not suitable for EGFR pharmDx testing. Use of DakoCytomation EGFR pharmDx on tissues processed with fixatives other than formalin has not been validated.
• Specimens from the biopsy, 3-4 mm thick, should be fixed for the appropriate time, routinely processed and paraffin embedded.
• Properly fixed and embedded tissue blocks expressing the EGFR protein will keep indefinitely prior to sectioning and slide mounting if stored in a cool place (15-25° C).

Methodology

EGFR pharmDx™ is a standard and reproducible immunohistochemistry test performed on routinely fixed, paraffin-embedded specimens. IHC staining allows the direct visualization of EGFR protein expressed on the surface of tumor cells. An automated staining platform utilized in our laboratory increases consistency and reproducibility of staining.

Quality Assurance

Our laboratory routinely utilizes several controls to ensure that each assay run has been performed appropriately and according to protocol specifications. Control slides and tissue sections are tested alongside a patient’s tissue sample each time the assay is performed.

1.	Positive and negative cell line controls indicate the validity of the staining run.
2.	A positive tissue section (known EGFR protein staining intensity), tested alongside each patient specimen, controls all steps of the analysis.
3.	Known negative tissues detect unintended antibody cross-reactivity to cells/cellular components.
4.	Evaluation of intrinsic controls avoids false negatives.
5.	Each patient tissue sample is tested with a negative control reagent to check for nonspecific background staining and to serve a baseline for evaluation of EGFR specific staining.

Interpretation

Experienced pathologists assess IHC staining in the tumor region of each patient’s specimen. EGFR pharmDx results are reported as positive or negative.

EGFR negative – absence of specific membrane staining within the tumor

EGFR positive – positive staining is defined as any IHC staining of tumor cell membranes above background level, whether it is complete or incompletecircumferential staining. Additional staining data is documented for informational purposes only, including staining intensity (weak, moderate or strong) and percent of tumor cells staining (> or equal to 1%).

Analytic Time

Within 24 hours from the receipt of the specimen, a faxed report is available followed by a printed copy.

CPT Code

88342

Background

Epidermal Growth Factor Receptor (EGFR) is a transmembrane receptor encoded by the human HER1 gene. EGFR protein contains an extracellular ligand binding domain, a transmembrane region and an intracellular domain with intrinsic protein tyrosine kinase activity.

EGFR is expressed by a variety of normal cells including many epithelial cell types. It is also expressed in solid tumors derived from these cells, including more than 70% of metastatic colorectal cancers, as well as, head and neck cancer, non-small cell lung cancer (NSCLC), pancreatic cancer, breast cancer, renal cell carcinoma, ovarian cancer and gliomas. EGFR overexpression frequently occurs in the absence of gene amplification. Epidermal Growth Factor Receptor plays a critical role in the growth of tumor cells, as well as in the DNA repair and survival of tumor cells damaged by chemo- and radiation therapy. Expression of the receptor correlates with poor prognosis, decreased survival, and increased metastasis.

Erbitux™ (cetuximab) is a chimeric (mouse/human) monoclonal antibody, which binds with high specificity and affinity to the extra cellular domain of the human epidermal growth factor receptor. As a result, certain growth factors are blocked from binding and signaling the cell to promote tumor cell growth, survival and progression.

Cetuximab is FDA approved for use in combination with irinotecan in the treatment of patients with EGFR-expressing metastatic colorectal cancer, who are refractory to irinotecan-based chemotherapy. It also approved for use as a single agent in the treatment of patients with EGFR-expressing, metastatic colorectal cancer who are intolerant to irinotecan-based chemotherapy. Cetuximab/irinotecan produced significantly greater efficacy than single-agent cetuximab. Efficacy is not determined by level of EGFR expression. The drug is reasonably well tolerated and is a promising new treatment option for patients with metastatic colorectal carcinoma.

For more information, contact your AmeriPath Territory Manager.

Phone 877.223.PATH
Email: apoclientservices@ameripath.com
Fax 508.664.8806

Links

For additional information, the following resources are available:

FDA News – FDA approves Erbitux for Colorectal Cancer

People Living With Cancer – News Center - Cancer Advances: News from the 2003 Annual ASCO Meeting