According to results recently presented at the 40th annual meeting of the American Society of Clinical Oncology (ASCO), the laboratory test called Oncotype DX, which has already been approved for determining the risk of a recurrence in breast cancer, may also help detect which patients with breast cancer will respond to chemotherapy. Results from Oncotype DX may help guide patients to the most effective individualized treatment options for their cancer.
Breast cancer is responsible for approximately 40,000 deaths annually in the United States alone. However, if breast cancer is detected early, prior to the spread of cancer, cure rates remain high. Although patients with early breast cancer derive a significant survival benefit overall with the addition of chemotherapy in their treatment regimen, some women may be exposed unnecessarily to chemotherapy, suffering from side effects caused by the treatment while gaining no benefit. By using a test such as Oncotype DX to determine whether a patient is likely to achieve benefit from chemotherapy and/or is likely to experience a cancer recurrence, physicians can tailor treatment to meet the needs of individual patients. This also allows patients who are not likely to benefit from specific chemotherapy agents to seek other treatment options.
Oncotype DX is a test that uses breast cancer biopsies, or small tissue samples, to determine whether a patient has breast cancer. The test analyzes the expression of specific genes or clusters of genes of the cancer cells and, through statistical analysis, can provide associations between the expression of one or more genes and specific outcomes of patients, such as risk of a cancer recurrence. Oncotype DX is used to determine the risk of a distant recurrence in women with node-negative, estrogen receptor-positive breast cancer through the evaluation of 21 genes.
Researchers from Italy recently conducted a study to further evaluate Oncotype DX and its ability to predict an anti-cancer response to chemotherapy in women with early breast cancer. Previous studies have indicated that a complete disappearance of cancer following treatment upon evaluation under a microscope of a tissue sample, referred to as a pathologic complete response, has been demonstrated to improve cancer-free and overall survival in previous clinical studies. The study included 89 patients who had their biopsy specimens analyzed by Oncotype DX prior to any treatment. The patients were initially treated with a taxane (Taxotere® or paclitaxel), followed by the surgical removal of their cancer, followed by further chemotherapy with a regimen referred to as CMF (cyclophosphamide, methotrexate, 5-fluorouracil), radiation therapy and tamoxifen (Nolvadex®) if they were estrogen receptor-positive. Twelve percent of patients achieved a pathologic complete response. The results from Oncotype DX identified the expression of 86 genes that were associated with the achievement of a pathologic complete response. Expression of these genes tended to be from 3 gene groups: an estrogen receptor group, an immune group and a proliferation group. Patients with a higher expression of genes in the estrogen receptor group had a significantly lower rate of a pathologic complete response, while patients with a high expression of genes from the immune group and proliferation group had a higher rate of a pathologic complete response. Furthermore, when compared to the genes that predict for the risk of a distant recurrence, patients at a higher risk for a recurrence also have significantly higher rates of a pathologic complete response following treatment.
The researchers concluded that Oncotype DX helps predict a pathologic complete response following chemotherapy for patients with early breast cancer. The fact that patients who are identified to be at a high risk for developing a distant recurrence also tend to achieve pathologic complete responses following therapy led to greater evidence that these patients will achieve improved survival with additional treatment. Further studies will help elucidate exactly which patients will benefit from specified therapeutic approaches, leading the field of oncology into individualized treatment for patients.
Reference: Gianni L, Zambetti M, Clark K, et al. Gene expression profiles of paraffin-embedded core biopsy tissue predict response to chemotherapy in patients with locally advanced breast cancer. Proceedings from the 40th annual meeting of the American Society of Clinical Oncology. 2004. Abstract #501.
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