Understanding Triple Negative Breast Cancer
In the last few years, health professionals have realized that breast cancer is not just one disease, but that there are many forms. The subtypes of breast cancer are generally diagnosed based upon the presence of three receptors known to fuel most tumors. These are estrogen receptors, progesterone receptors and human epidermal growth factor receptor 2 (HER2). The most successful treatments for breast cancer, including Herceptin and Tamoxifen, target these three receptors. In triple negative breast cancer (TNBC), none of these three receptors are found, thus the name “triple negative”.
Of the 190,000 new cases of breast cancer diagnosed in the United States each year, about 10 to 20% are triple-negative. It is more prevalent among pre-menopausal and African-American women. It is a fast-growing cancer that has a higher risk of recurrence in the first three to five years after diagnosis. The average survival time for TNBC after recurrence is only nine months.
An estimated 65 to 90% of triple negative cancers are basal-like tumors and associated with mutations in the BRCA1 gene. They typically have a poorer prognosis than non-basal tumors.
Depending upon the stage of diagnosis, triple negative breast cancer can be extremely aggressive, and more likely to metastasize than other subtypes of breast cancer. After surgery and radiation treatments, it is typically responsive to chemotherapy - a combination of three medications called ACT, which stands for Adriamycin, Cytoxan, and Taxol.
Avastin has been used in clinical trials to treat TNBC. Avastin blocks blood vessel growth to tumors by inhibiting a growth-inducing protein called vascular endothelial growth factor, or VEGF. Without VEGF the tumors are starved of nutrients. Avastin is approved for multiple cancers, including HER-2 negative breast cancer, brain, lung, colorectal, and kidney cancers.
A recent phase three clinical trial showed that adding Avastin to Taxol doubled the survival rate of metastatic breast cancer patients to 11.8 months, compared to 5.9 months with Taxol alone. Overall survival rates did not change. Further clinical trials continue, but may not have results for several years.
Another experimental class of drugs called PARP inhibitors may have potential for the treatment of TNBC. The drugs block the ability of the damaged cells to repair themselves, causing cancer cells to die off or become more susceptible to chemotherapy. The first study of the new drugs involved 116 women with metastatic disease. Tumors shrank in 48% of patients treated with PARP inhibitors, compared with 16% of patients on chemotherapy alone.
The Triple Negative Breast Cancer Foundation was founded in 2005 to raise awareness and support research in the area of TNBC.
Sources Include: The Triple Negative Breast Cancer Foundation and the American Cancer Socity.