Gene Expression Profiling Predicts Response of Breast Cancer to Chemotherapy

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Breast Cancer and Chemotherapy Response

According to a study published in the Journal of Clinical Oncology, gene expression patterns may predict chemotherapy response in women with locally advanced breast cancer.

After lung cancer, breast cancer is the second leading cause of cancer death in women. According to the American Cancer Society, an estimated 211,240 women will be diagnosed with breast cancer in 2005 and 40,410 will die of the disease. Locally advanced breast cancer refers to breast cancers that are large or that have spread to lymph nodes, skin or muscle near the breast.

The laboratory technique of gene expression profiling offers promise for guiding the diagnosis and treatment of cancers including breast cancer. This technique tests cancer cells for specific patterns in their gene activity or in proteins produced by the genes. The identified patterns tend to be strongly associated with a specific type of cancer and specific characteristics of the cancer, such as aggressiveness or response to therapy.

Gene expression profiling may allow for more individualized cancer therapy by identifying those patients who are most or least likely to respond to a particular type of therapy.

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In order to determine whether gene expression profiling predicted response to chemotherapy among women with locally advanced breast cancer, researchers assessed the expression of 384 genes in 89 breast cancer patients in Italy.

Patients were treated with the chemotherapy drugs paclitaxel and doxorubicin before surgery. After surgery, pathologic examination of the removed tissue provided information about how the cancer had responded to chemotherapy. Eleven women were found to have had a complete response to chemotherapy, meaning that chemotherapy had completely eliminated the cancer.

Eighty-six of the 384 examined genes were found to be associated with the probability of complete response to chemotherapy. Higher expression of proliferation-related and immune-related genes, and lower expression of estrogen-receptor-related genes, increased the probability of a complete response. Generally similar results were found in an independent sample of 82 patients from the M.D. Anderson Cancer Center in Texas.

The researchers conclude that the level of expression of certain types of genes may provide information about the likelihood of chemotherapy response in women with locally advanced breast cancer.

Reference: Gianni L, Zambetti M, Clark K et al. Gene expression profiles in paraffin-embedded core biopsy tissue predict response to chemotherapy in women with locally advanced breast cancer. Journal of Clinical Oncology. 2005;23:7265-7277.

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