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MammaPrint: Molecular-targeted Breast Prognostic Test
The genetic analysis of MammaPrint predicts which women will have a greater chance of breast cancer recurrence, 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.
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. Existing methods can't distinguish the patients with a high risk for recurrence from those with low risk with camparable accuracy.
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 have been mostly or totally ineffective at identifying clinical responders to various therapies.
The molecular MammaPrint laboratory test is a tool for the oncologist. The oncologist should take advantage of all the tools available to him/her to evaluate 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.
The combination of these tests can enhance the ability to distinguish between "low" risk and "high" risk patients. Patients in the "low" risk group can be spared the unnecessary toxicity, particularly associated with ineffective treatment, while those in the "high" risk group, who would benefit from chemotherapy can 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 and overall survival.
Every breast cancer patient should have their own unique evaluation 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.
Sources:
N Engl J Med 347:1999-2009, 2002
J Intern Med 264:275-287, September 2008
About the AngioRx Assay in breast cancer:
ER and PR tests in breast cancer, which detect only VEGF expression, or even overexpression, are valuable not because they measure expression of estrogen and progesterone but rather because they detect (and supposedly measure) the ER and PR receptors in the nucleus. The presence of positive IHC staining of such receptors in at least 10% of nuclei implies that the tumor is hormonally dependent and that, therefore, depriving the cells of the hormone will kill them or retards their growth.
Unlike a test for the presence of receptors to a specific antigen, which only "implies" dependence upon that antigen, an AngioRx assay is functional in that it actually assesses the direct or indirect effect of the drug upon the cell, whether it is a tumor cell or an endothelial cell. VEGF just happens to be one molecule which has been implicated in the process but there may be more.
If it were the only protein involved, then one would expect that VEGF expression would correlate with Avastin activity 100% of the time but it actually does so only about 20% of the time. The AngioRx assay doesn't just focus on VEGF or any one protein or mechanism. Whether it's VEGF alone (unlikely) or in combination with other proteins and other mechanical factors, the assay works by assessing the net effect of all those factors.
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