Biomarkers are any trait of a tumor that can be tested to help categorize or assess the tumor. Tests for the presence of hormone receptors, and the amplification of certain genes such as HER-2, can help predict how the tumor might behave with and without treatment. Biomarkers can guide treatment decisions and options for care. For example a tumor that shows amplification (too many copies) of the gene HER-2 is more likely to respond to the antibody trastuzumab. This is one of the most successful biomarkers in breast cancer treatment today. Cell function is extremely complex and targeted breast cancer treatment refers to treatments that are directed at specific parts of the cell machinery such as the HER-2 dependent or the estrogen dependent pathways. Major efforts are underway to learn more about the details of how cancer cells turn on and off so that targets can be identified for possible treatment development.
If the doctor refers to your cancer as a triple negative tumor, it means that you have an estrogen- and progesterone- receptor-negative tumor and also a HER-2 negative tumor. In other words, your tumor is not going to benefit from hormone treatments or trastuzumab (Herceptin). With fewer tools to use as treatment, these cancers at present have only cytotoxic chemotherapy as possible systemic treatment options.