The genetic analysis of Oncotype DX predicts which women will have a greater chance of breast cancer recurrence. The test looks at 21 genes that influence the behavior of breast cancer cells. Until this test, it had been difficult to pinpoint which women would benefit most from chemotherapy, and those which wouldn’t.
MammaPrint is another genetic test that could help patients with early-stage breast cancer predict their chance of relapse, information that could save many patients from unnecessary chemotherapy. This test looks at the expression of 70 genes linked to breast cancer with an accuracy level of 96.7% as determined by a study published in the New England Journal of Medicine.
Another molecular-targeted breast prognostic test called Mammostrat, is validated with the usual, retrospective, non-randomized study using archival tissues and uniform batch processing and slide interpretation. It utilizes five immunohistochemical (IHC) biomarkers to classify patients into high, moderate, or low-risk categories for disease recurrence.
These new gene expression profiling tests enable the oncologist and breast cancer surgeon to more accurately determine who should be treated and who should not be treated with chemotherapy, but they cannot predict chemo response.
These laboratory tests are 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 (and even less for "targeted" drugs), 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.
These tests 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 with a "functional" bio-marker 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.
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.
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