MammaPrint Breast Cancer Gene Test Okayed by US FDA
Wednesday February 7, 2007
For women with early-stage breast cancer, one worry is always "will it come back?" The US Food and Drug Administration has okayed the marketing of a gene test, MammaPrint, which measures the activity of 70 genes that predict the chances of a relapse. Used in Europe since 2005, the test shows the possibility of breast cancer's return within five to ten years of initial diagnosis. It takes several factors into the equation: tumor size of five centimeters or less, clear lymph nodes (no metastasis), and age 61 and younger. If you have this test, it may help you decide what kind of treatment and follow-up to take for breast cancer.
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Another new test, that looks at the expression of 70 genes linked to breast cancer, can accurately assess a patient’s risk of recurrence or death. The correlations of this are vastly superior to those obtained with standard prognostic markers.
The 70 genes in a woman’s tumor analyzed by MammaPrint predict the 10-year survival of the patient at a significance level over three times greater than existing methods and with an accuracy level of 96.7% as determined by a study published in the New England Journal of Medicine.
Existing methods can’t distinguish the patients with a high risk for recurrence from those with low risk with comparable accuracy. This new gene expression profiling test enables the oncologist and breast surgeon to more accurately determine who should be treated.
This test has been shown to be superior over conventional assessment of risk of future metastatic disease, such as histological assessment of tumor aggressiveness (by grade). However, one gets more accurate information when using intact RNA isolated from “fresh” tissue than from using degraded RNA, which is present in paraffin-fixed tissues.
For the vast majority of cancer patients, the cancer will not recur regardless of whether they receive chemotherapy. So they are exposed needlessly to the treatment, which can cause myelosuppression, mucositis, cardiac problems, peripheral neuropathy, central neurotoxicity, or leukemia. Doctors cannot tell, however, which patients needed the chemotherapy.
This laboratory tests is a tool for the oncologist. The oncologist should take advantage of all the tools available to him/her to treat a patient. And since studies show that only 25-30% of patients do respond to chemotherapy that is available to them, there should be due consideration to looking at the advantage of molecular and cellular assay tests to the resistance that has been found to chemotherapy drugs.
Because of this, there is a good portion of cancer patients that are either undertreated or overtreated because there was no adequate information on who will recur. This test can enhance the ability to distinguish between low risk and high risk patients. Patients in the high-risk group, who would benefit from chemotherapy can then be pre-tested to see what treatments have the best opportunity of being successful, and offers a better chance of tumor response resulting in progression-free survival, while those in the lower-risk groups can be spared the unnecessary toxicity, particularly associated with ineffective treatment.
This test has enormous implications for the short-term future of cancer research in general, and is one of the truly great cancer breakthroughs of our time. This DNA microarray will prove to be highly complementary to the parellel breakthrough efforts in targeted therapy through cell culture assays like the EGFRx™ Assay.
Cell Culture Assays can prospectively report to a physician specifically which chemotherapy agent would benefit a high risk cancer patient by testing that patient’s live cancer cells. Drug sensitivity profiles differ significantly among cancer patients even when diagnosed with the same cancer. Knowing the drug sensitivity profile of a specific cancer patient allows the treating oncologists to prescribe chemotherapy that will be the most effective against the tumor cells of that patient.
Every breast cancer patient should have her own unique chemotherapy trial based on consultation of pathogenic profiles and drug sensitivity testing data. Research and application of these tests are being encouraged by growing patient demands, scientific advances and medical ethics. These tests are not a luxury but an absolute necessity, and a powerful strategy that cannot be overlooked.