Why HER2 Testing is Important

Test results have important treatment implications 1

Accurate testing allows identification of appropriate patients for Herceptin (trastuzumab)

  • Published studies show that 20-25% of all breast cancers are HER2+. 6-10
  • Studies have consistently shown that HER2 overexpression is associated with decreased overall survival and a lowered response to chemotherapy and hormonal therapy. 11,12
  • HER2 overexpression continues throughout the course of the disease and drives aggressive tumor growth.6,13,2

Because of Herceptin's significant clinical benefits in extending survival for HER2+ breast cancer patients, it is important to accurately determine the HER2 status of all patients with breast cancer.

  • An exploratory analysis of DFS, based on results from NSABP B-31 quality assurance testing, showed:
  • On average, patients with tumors testing IHC 3+ and FISH+ received significant DFS benefit from treatment with Herceptin
  • Mean benefits were smaller in subgroups in which FISH and IHC results differed, but definitive conclusions cannot be drawn due to the small number of events

HER2 testing recommended for all patients

  • Determination of HER2 status is recommended for all patients with invasive breast cancer by:
  • American Society of Clinical Oncology (ASCO) 3
  • College of American Pathologists (CAP) 4
  • National Comprehensive Cancer Network® (NCCN) 5
  • HER2+ status may indicate either gene amplification or protein overexpression
HER2 gene amplification and protein overexpression

The excess copies of the HER2 gene result in the continuous overexpression of the HER2 protein on the cell surface 2

HER2 Testing Best Practices and Summarized Findings

IHC detects HER2 overexpression at the protein level, and may be affected by conditions of the testing procedures. These include: time to fixation, duration of fixation, processing, denaturation, heating, antigen retrieval, the staining procedure used, and the interpretation of staining.15,16 Although there are antigen retrieval techniques in use, these may result in false-positive IHC results. FISH measures HER2 DNA. Some fixatives, chemicals or heat, may interfere with the FISH assay. However, aninternal control is used to distinguish between a FISH-negative and a non-informative result.10 Scoring difficulties associated with FISH testing may be caused by difficulties in identifying specific invasive cells to include in the determination.

HER2 testing should be performed by laboratories with demonstrated proficiency in the specific technology being utilized. Improper assay performance may result from the use of suboptimally fixed tissue, failure to utilize specified reagents, deviation from specific assay instructions, and failure to include appropriate controls for assay validation and can lead to unreliable results.1,18

Recent findings suggest the need to improve quality control measures in laboratories that use IHC assays, including periodic testing for concordance with FISH. These studies also suggest that large-volume reference laboratories performing HER2 tests are more reliable than small-volume laboratories.15,19 HER2 testing should be done in laboratories accredited to perform such testing. Ongoing proficiency testing is a necessary component of a laboratory's qualification for accreditation.

Concordance with central lab correlated with greater testing experience 17

Rates of discordance were lower for labs with greater experience performing the test*

Graph: Discordance rates by lab experience

*Discordance defined as differing HER2 test result between initial local testing and follow-up central testing as part of quality assurance protocol. Central lab tested IHC by HercepTest and FISH by PathVysion.

Labs are required to demonstrate proficiency in specific assays to maintain CAP accreditation 3,4

Collaboration is key among specialists

Collaboration among specialists-including pathologists, surgeons, radiologists, and oncologists-is critical to help ensure accurate interpretation of results and appropriate disease management

Medical Society Guidelines on HER2 Testing

NCCN® and ASCO recommend HER2 testing for all patients with invasive breast cancer and recommend confirming IHC 2+ results with FISH.*,8

*IHC=immunohistochemistry; FISH=fluorescence in situ hybridization

  • References:
  • 1. Herceptin® (trastuzumab) Full Prescribing Information, Genentech, Inc. May 2008.
  • 2. Sliwkowski MX, Lofgren JA, Lewis GD, Hotaling TE, Fendly BM, Fox JA. Nonclinical studies addressing the mechanism of action of trastuzumab (Herceptin). Semin Oncol. 1999;26 (suppl 12): 60-70.
  • 3. Wolff AC, Hammond EH, Schwartz JN, et al. American Society of Clinical Oncology/College of American Pathologists Guideline Recommendations for Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer. JClin Oncol.2007;25:118-145.
  • 4. Wolff AC, Hammond ME, Schwartz JN, et al. American Society of Clinical Oncology/College of American Pathologists Guideline Recommendations for Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer. Arch Pathol Lab Med.2007;131:18-43.
  • 5. National Comprehensive Cancer Network. Clinical Practice Guidelines in Oncology: Breast Cancer. Version 1; 2007. Available at: http://www.nccn.org. Accessed September 2, 2008.
  • 6. Konecny G, Pauletti G, Pegram M, et al. Quantitative association between HER-2/neu and steroid hormone-receptors in hormone receptor-positive primary breast cancer. J Natl Cancer Inst. 2003;95:142-153.
  • 7. Slamon DJ, Clark GM, Wong SG, et al. Human breast cancer: correlation of relapse and survival with amplification of the HER-2/neu oncogene. Science. 1987;235:177-182.
  • 8. Slamon DJ, Godolphin W, Jones LA, et al. Studies of the HER-2/neu proto-oncogene in human breast and ovarian cancer. Science. 1989;244:707-712.
  • 9. Pegram M, Slamon DJ. Biological rationale for HER2/neu (c-erbB2) as a target for monoclonal antibody therapy. Semin Oncol. 2000;5(suppl 9):13-19.
  • 10. Pauletti G, Godolphin W, Press MF, Slamon DJ. Detection and quantitation of HER-2/neu gene amplification in human breast cancer archival material using fluorescence in situ hybridization. Oncogene. 1996;13:63-72.
  • 11. Paik S, Hazan R, Fischer ER, et al. Pathologic findings from the National Surgical Adjuvant Breast and Bowel Project: prognostic significance of erbB-2 protein overexpression in primary breast cancer. J Clin Oncol. 1990;8:103-112.
  • 12. Ross JS, Fletcher JA. HER2/neu (c-erb-B2) gene and protein in breast cancer. Am J Clin Pathol. 1999;112(suppl 1):S53-S67.
  • 13. Simon R, Nocito A, Hubscher T, et al. Patterns of HER-2/neu amplification and overexpression in primary and metastatic breast cancer. J Natl Cancer Inst. 2001;93:1141-1146.
  • 14. Bast RC Jr, Ravdin P, Hayes DF, et al. 2000 Update of recommendations for the use of tumor markers in breast and colorectal cancer: clinical practice guidelines for the American Society of Clinical Oncology. J Clin Oncol. 2001;19:1865-1878.
  • 15. Paik S, Bryant J, Tan-Chiu E, et al. Real-world performance of HER2 testing ?National Surgical AdjuvantBreast and Bowel Project experience. J Natl Cancer Inst. 2002; 94:852-854.
  • 16. O'Leary TJ. Standardization of immunohistochemistry. Appl Immunohistochem Mol Morphol. 2001; 9:3-8
  • 17. Paik S, Bryant J, Tan-Chiu E, et al. Real-world performance of HER2 testing - National Surgical Adjuvant Breast and Bowel Project experience. J Natl Cancer Inst. 2002;94:852-854.
  • 18. Roche PC, Suman VJ, Jenkins RB, et al. Concordance between local and central laboratory HER2 testing in the Breast Intergroup Trial N9831. J Natl Cancer Inst. 2002;94:855-857.
  • 19. Roche PC, Suman VJ, Jenkins RB, et al. Concordance between local and central laboratory HER2 testing in the Breast Intergroup Trial N9831. J Natl Cancer Inst. 2002; 94:855-857.
  • 20. Shan K, Lincoff AM, Young JB. Anthracycline-induced cardiotoxicity. Ann Intern Med.1996;125(1):47-58.23.


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