The location of the tumor within the breast is an important prognostic factor. Tumors that develop toward the outside of the breast tend to be less serious than those that occur more toward the middle of the breast.
Hormone Receptor-Positive or -Negative
Breast cancer cells may contain receptors, or binding sites, for hormones like estrogen or progesterone. Cells containing these binding sites are known as hormone receptor-positive cells and if they lack them are called hormone receptor-negative cells.
Hormone receptor-positive cells grow more slowly than receptor negative cells. Women have a better prognosis if their tumors are receptor-positive because these cells grow more slowly than receptor-negative cells and they have more treatment options. (Hormone receptor-negative tumors can be treated only with chemotherapy.)
The Influence of Genes
Determining a "genetic signature" for a tumor may prove to be a very powerful predictor of the aggressive nature of a breast cancer. Researchers have focused on 70 genes whose activity patterns may help make such predictions.
The relevance of the inherited BRCA1 or BRCA2 mutations to survival is controversial. Some studies have suggested that these mutations offer a survival advantage, while others suggest that they make no difference or even worsen prognosis. Women with these genetic mutations do have a greater risk for a new cancer to develop. Patients with BRCA1 mutations tend to develop tumors that are hormone receptor negative, which can behave more aggressively.
Tumor Markers
Researchers are investigating numerous substances in tumor cells that may indicate whether or not a cancer is likely to spread. Such chemical markers may help doctors determine treatments, and some may even prove to be targets for future drugs. The following are only a few of the more well-researched markers.
HER-2. The HER-2 protein is part of the epidermal growth factor receptor family and is becoming an important marker in breast cancer. It is involved in the growth and spread of breast cancer cells, and about 25 - 30% of patients with breast cancer have high levels of this protein. The presence of HER-2 may suggest aggressive cancer. It is proving to be important in determining treatment choices. For example, women who have HER-2 positive cancers tend to benefit from anthracycline-based chemotherapy.
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