MRS is a method of diagnosing breast cancer using biological factors, such as metabolism, that are intrinsic properties of the disease, not possible by imaging the anatomy of the breast. Comparison of the MR spectroscopic technique with the fine-needle aspiration biopsy findings in lymph nodes revealed a sensitivity of 82 percent, specificity of 100 percent, and accuracy of 90 percent.55

As with an MRI exam, MRS does not expose the patient to radiation, and takes about 45 minutes to perform. However, this technique is expensive and unproven, and therefore limited to academic medical centers conducting research in this area.

Gene Profiling

Genetic profiling allows for the characterization of a tissue sample based upon the genetic makeup and activity of the sample. For example, tissue samples from an invasive cancer and from a benign cyst will have very different growth characteristics determined by the genetic makeup of the tissue and more importantly the expression of that genetic code (the relative level of gene activity). The relative activity of thousands of genes on a microarray (glass slide with many spots each individually representing one gene) can be analyzed by computer algorithms to predict the behavior of the tissue. A recent study (2002) demonstrated the potential of genetic profiling to predict the clinical outcome of breast cancer.51 Microarray DNA expression profiles can be used on primary breast tumors to identify a signature expression profile (“poor prognosis signature”) of 70 genes strongly predictive of a short interval to distant metastases (<5 years). The “poor prognosis signature” consists of genes regulating cell cycle, invasion, metastasis, and angiogenesis. The gene expression profile outperformed all currently used clinical parameters in predicting outcome of disease, such as lymph node status and histological grade. A large unselected “cohort” of breast cancer patients may be required to validate the findings and bring this approach closer to the clinic. Eventually this technique may be used to select patients who would benefit from adjuvant therapy and avoid ineffective treatments. This approach may also prove useful in assessing prognosis prior to biopsy, helping to reduce the number of open surgical biopsies of benign tissue.

Genetic Testing

Many cases of hereditary breast cancer are due to mutations in either the BRCA1 or the BRCA2 gene. The BRCA genes are tumor suppressor (control the growth of cells) genes that in their mutated forms become cancer susceptibility genes increasing the risks of developing breast and



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