The test, called Oncotype DX, was approved by the U.S. Food and Drug Administration (FDA) in January, 2004 for use in patients with node-negative, estrogen-receptor (ER)- positive breast cancer who are taking post-surgical (also called adjuvant) tamoxifen therapy.
Oncotype DX is an example of "individualized oncology," whose goals are to match cancer patients with appropriate therapy in order to spare certain patients from the side effects of chemotherapy, improve quality of life, and provide better outcomes. The specific purpose of the Oncotype DX test is to determine which patients with node-negative, estrogen-receptor (ER)- positive breast cancer who are taking adjuvant tamoxifen therapy will require post-surgical (i.e., adjuvant) chemotherapy.
If your breast cancer did not extend to the lymph nodes (and was therefore classified as node-negative), was of the ER-positive type, and you will be taking tamoxifen therapy after your surgery, then you can consider having the Oncotype DX test. For the test, a sample of your biopsy specimen is sent to the laboratory of Genomic Health, the biotechnology company who developed and performs the Oncotype DX test. In the Oncotype DX test, which is a genomic type of test, a panel of 21 genes in the breast cancer cells are examined to determine which of the genes are active.
Based on which of the genes in the breast cancer cells are active, a patient is categorized into having a certain likelihood of recurrence of breast cancer at a distant site by 10 years after surgery. In the Oncotype DX test, the categories of risk of recurrence are low, intermediate, and high.
Most of the 668 patients with node-negative, ER-positive breast cancer and who received post-surgical tamoxifen, but not post-surgical chemotherapy, and whose stored breast cancer cells were examined in a recent study of the Oncotype DX test were classified as having a low risk of recurrence. The following table shows the percentages of patients in the different categories of risk and the actual recurrence observed by 10 years after surgery.
Category of Risk % of Patients % of Patients in
of Recurrence Based in Category Category Who Had
on Gene Activity in Distant Recurrence
Breast Cancer Cells at 10 Yrs After
Surgery
Low 51% 6.8%
Intermediate 22% 14.3%
High 27% 30.5%
By predicting the degree of risk of recurrence, the Oncotype DX test can help breast cancer patients and oncologists select the most appropriate types of post-surgical treatment for the individual patient.
If you choose to take the Oncotype DX test, and you are classified as low-risk based on results of your test, then you may be able to avoid having chemotherapy after surgery. Discuss options for post-surgery treatment with your oncologist, so that you and your oncologist select the types of therapy that are the best for you.
If you choose to take the Oncotyoe DX test, and you are classified as low-risk based on results of your test, then your oncologist may recommend a combination of post-surgical tamoxifen and chemotherapy, in order to reduce your risk of recurrence. Discuss options for adjuvant treatment with your oncologist, so that you and your oncologist select the types of therapy that are effective in reducing risk of recurrence and are the best for your needs.
If your breast cancer extended to the lymph nodes (therefore classified as node-positive) and/or was of the ER-negative type, then the Oncotype DX test is not appropriate for you. Discuss options for post-surgical treatment with your oncologist, so that you and your oncologist select the types of therapy that are the best for you.
REFERENCES
1. S. Russell. High hopes over test for breast cancer; Redwood City lab gauges likelihood of recurrence.
San Francisco Chronicle. 12/11/04.
2. S. Paik, S. Shak, G. Tang, C. Kim, et al. A multigene assay to predict recurrence of tamoxifen-treated, node-negative breast cancer. New England Journal of Medicine. 2004; 351(27):2817-2826.
3. R.C. Bast, Jr. and G. N. Hortobagyi. Individualized care for patients with cancer — a work in progress. New England Journal of Medicine. 2004; 351(27):2865-2867.
4. M. Fox. Test shows who needs chemo for cancer. 12/11/04. Accessed at www.reuters.com.
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