As a category, multiparameter gene expression tests for breast cancer are relatively new, although their use is increasing. They require a minimum quantity of tumor tissue and specific sample processing. Many of these assays are effective in tissue that has been preserved in some way and stored for a period of time (archival tissue), which allows for the evaluation of patients well after surgery. All of them are currently intended to be used only on cancers that have not yet spread to the lymph nodes, and each has been developed to be used in specific populations of patients. They have the potential of helping to identify those with the highest and lowest risk of breast cancer recurrence.
- MammaPrint® test
- Evaluates the expression profile of 70 genes
- Cleared for marketing by the U.S. Food and Drug Administration (FDA)
- For newly diagnosed patients with Stage I or II breast cancer that is equal to or less than 5 centimeters (2 inches) and has not spread to the lymph nodes
- Preserved, fresh or frozen breast tissue sample
- Categorizes women into a high versus low risk for recurrence within 10 years but does NOT predict benefits from adjuvant chemotherapy
- Available from locations in the U.S. and in the Netherlands
- Oncotype DX®
- Evaluates the expression profile of 21 genes
- For newly diagnosed patients who have Stage I or II breast cancer that is estrogen receptor positive and has not spread to the lymph nodes
- Preserved tumor tissue
- Used to predict the risk of recurrence in patients treated with tamoxifen and assesses the benefit of other chemotherapy regimens (i.e., CMF, methotrexate/5-fluorouraci/leucovorin)
- Included in the American Society of Clinical Oncology (ASCO) 2007 Update (Recommendations for the Use of Tumor Markers in Breast Cancer), in guidelines from the National Comprehensive Cancer Network (NCCN), and is addressed by the National Breast Cancer Coalition (NBCC)
- Commercially available from one laboratory
Many other multi-gene or multi-gene expression assay systems have been developed. ASCO, NCCN, and other professional organizations maintain that the MammaPrint® test and others, such as the Rotterdam Signature and the Breast Cancer Gene Expression Ratio, are promising but that none are currently sufficiently validated to warrant inclusion into standard guidelines for the management of patients with breast cancer.
Clinical trials are currently underway to address the use of these assays:
- The TAILORx (Trial Assigning Individualized Options for Treatment) trial is comparing adjuvant hormonal therapy with adjuvant chemohormonal therapy in women with an Oncotype DX intermediate risk Recurrence Score.
- The RxPONDER (Rx for Positive Node, Endocrine Responsive Breast Cancer) is designed to confirm that breast cancer that is ER-positive and has spread to a lymph node (node-positive) can be successfully treated with hormonal therapy with or without chemotherapy based on the Oncotype DX risk scores.
- The MINDACT (Microarray In Node-Negative Disease may Avoid Chemotherapy) trial is comparing the MammaPrint test with certain traditional (clinical and pathologic) criteria in assigning patients to chemotherapy treatment.
All of these trials, and future trials, will further delineate the clinical usefulness of the tests and will evaluate their ability to help guide breast cancer therapy. While it will be a number of years before results from trials are conclusive, health care providers may decide to use these molecular tests in monitoring and treating patients with breast cancer on an individual basis. If you would like to know more, talk to your health care provider about whether one of these tests might be right for you.
For additional details on these and other similar tests, visit the following web sites: