A recent presentation at the 2005 meeting of the American Society of Clinical Oncology reveals that a test known as Oncotype DX can predict outcomes for women diagnosed with localized hormone receptor positive breast cancer.
Breast cancer is a malignancy associated with the tissues of the breast. A breast cancer diagnosis is followed by various tests that further describe the features of the cancer. One of these tests determines if the cancer was supported by the hormones estrogen and progesterone. If so, treatment may consist of drugs that prevent the hormones from reaching the breast cancer cells.
The Oncotype DX is a test performed on paraffin-embedded tissue that identifies 21 genes which have been associated with the outcome of early stage breast cancer. (Early stage breast cancer has not spread to the lymph nodes and is treated with surgery followed by hormonal therapy, adjuvant chemotherapy, radiation therapy or no therapy.) While previous reports of the test’s accuracy have been published, this recent presentation described the test’s ability to predict the outcome of hormone receptor positive breast cancer, even if the patient has not been treated with the long-standing hormonal treatment for breast cancer, Nolvadex (tamoxifen).
In this recent study, researchers used a recurrence scoring system (low, intermediate or high risk for recurrence) to determine the risk of recurrent breast cancer among women with estrogen receptor positive breast cancer. The scoring system was developed using the Oncotype DX test, which identifies 21 genes. Oncotype DX is also is a more sensitive predictor of estrogen receptor than standard tests. In addition to estrogen receptor, the proliferation gene group was also important in predicting outcomes. These values were then used to better predict the benefit of tamoxifen.
Results of the study indicate that the scoring system succeeded in determining which patients would benefit from further therapy in addition to tamoxifen. For example, patients in the high risk group had a 30 percent chance of relapsing whether or not they received tamoxifen-this indicates that this group should receive adjuvant chemotherapy in addition to tamoxifen.
Researchers believe that other genes also impact disease outcomes, although this new data confirms that Oncotype DX has an increasingly important role in the clinical assessment of estrogen receptive breast tumors, which may help in determining appropriate therapy.
Paik S, Shak S, tang G, et al. Expression of the 21 genes in the Recurrence Score assay and tamoxifen clinical benefit in the NSABP study B-14 of node negative receptor positive breast cancer. Proceedings from the 41st Annual Meeting of the American Society of Clinical Oncology. Orlando FL. 2005; Abstract #510.
Paik S, Shak S, Tang G, et al. A multigene assay to predict recurrence of tamoxifen-treated, node-negative breast cancer. New England Journal of Medicine. 2004 ;351:2817-2826.
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