Posted on March 8th, 2009 by
Oncotype DX® Accurately Determines HER2 Status in Breast Cancer
Oncotype DX® appears to determine HER2 status as accurately as standard laboratory testing methods. By the end of 2008, Genomic Health intends to provide HER2 status with results from all Oncotype DX testing. These results were recently presented at the 2008 American Society of Clinical Oncology (ASCO) Breast Meeting.
The majority of breast cancers are hormone receptor-positive. These cancers are stimulated to grow by the circulating female hormones estrogen and/or progesterone. Treatment of hormone receptor-positive breast cancer often involves hormonal therapies that suppress or block the action of estrogen. These therapies include tamoxifen [Nolvadex®] as well as agents known as aromatase inhibitors. Tamoxifen acts by blocking estrogen receptors, whereas aromatase inhibitors suppress the production of estrogen in postmenopausal women.
In order to determine whether hormonal therapy is likely to benefit a particular woman, it is necessary to accurately assess the hormone receptor status of the cancer. Currently, the standard test for hormone receptor status uses a procedure known as immunohistochemistry (IHC). It’s possible, however, that newer types of tests may provide comparable information about hormone receptor status along with additional information that that can aid in treatment planning.
Oncotype DX is a genomic test that that has been validated for use in women with newly diagnosed, Stage I or II, node-negative, estrogen receptor (ER)-positive breast cancer. Studies have also suggested that the test may be useful for women with node-positive breast cancer. The test predicts risk of cancer recurrence as well as likely benefit from adjuvant chemotherapy. It evaluates the activity of 21 genes from a sample of the patient’s cancer to determine the patient’s Recurrence Score. The Recurrence Score ranges from 0 to 100, with a higher score indicating a greater risk of recurrence. Oncotype DX continues to be evaluated for other uses in addition to its current indication.
Several types of cancers overexpress the human epidermal growth factor receptor 2 (HER2), including approximately 25-30% of breast cancers. HER2 is part of a biological pathway involved in growth and spread of cancer cells, and cancers that overexpress HER2 are referred to as HER2-positive. Overexpression of HER2 often results in uncontrolled growth and spread of cancer cells. It is now recommended that all breast cancer patients are tested for HER2 status before beginning treatment, as agents targeted against HER2 are available and tend to improve outcomes for patients overexpressing HER2. Standard testing for HER2 includes IHC and fluorescence-in-situ hybridization (FISH) testing.
Researchers recently conducted two studies to explore the accuracy of Oncotype DX in establishing HER status when compared with standard IHC or FISH testing among breast cancer patients.
The first study analyzed data from 755 patients who were enrolled in the Intergroup study E2197. These patients had cancer spread from zero to three axillary lymph nodes; HER2 status was compared between IHC and Oncotype DX testing. There was a 95% agreement regarding HER2 status between the two types of testing.
The second study evaluated data from a previous clinical trial conducted by researchers from Kaiser Permanente, the University of California, San Francisco and PhenoPath, Inc. The study included 568 patients and compared HER2 status between FISH and Oncotype DX testing. There was a 97% overall agreement between the two methods of testing.
The researchers concluded: “Based on this research demonstrating the accuracy and reliability of HER2 measurement using RT-PCR, Oncotype DX can provide additional patient-specific information and insight into each patient’s individual tumor biology.”
Patients diagnosed with early breast cancer may wish to speak with their physician regarding their individual risks and benefits of undergoing testing with Oncotype DX.
Reference: Genomic Health. Genomic Health Announces Data Supporting Use of Oncotype DX® to Accurately Assess HER2 Gene Expression in Breast Cancer Patients [press release]. Available at: http://investor.genomichealth.com/ReleaseDetail.cfm?ReleaseID=332727. Accessed September 2008.
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