What is Breast Cancer? Cancer occurs when, for unknown reasons, cells become abnormal and divide without control or order. If the cells that are growing do not have the ability to invade surrounding tissue or spread to other parts of the body, the tumor is benign (not cancerous). If the cells do not function like the body's normal cells, and invade healthy tissue and spread, then the tumor is malignant (cancerous). Breast cancer is a malignant tumor that has developed from cells of the breast.1,2
Researchers now understand that breast cancer is not one disease, but many different diseases. Even when tumors are classed together based on their appearance, they can act differently because of different genetic makeup. Only recently have researchers begun to understand this and to use it in predicting how a disease will progress — for example, the likelihood of a tumor to grow, spread or recur. This is an important new area of research.1,2
HER2-positive disease is one type of breast cancer. Characterized by aggressive growth and a poorer prognosis, it is caused by the presence of excessive numbers of a gene called HER2 (human epidermal growth factor receptor-2) in tumor cells.3 Some types of breast cancer are known as "hormone-receptor-positive" breast cancer. Some of these types of breast cancer cells have receptors for the hormone estrogen and are called "ER-positive," others have receptors for the hormone progesterone and are called "PRpositive." Cells that do not have such receptors are "negative" for these hormones.
What Causes Breast Cancer? Causes are unknown but risk factors for breast cancer exist and include: history of previous breast cancer, direct family history of breast cancer, inheritance of specific genes that cause breast cancer, certain pre-cancerous breast lesions, age at childbirth (first child after age 30 or never having children), early menstruation, late menopause, obesity, other cancer in the family, etc.4
How Many Women Develop Breast Cancer? According to the American Cancer Society, 178,480 women will be diagnosed with breast cancer in 2007, and 40,460 will die from the disease.5 HER2-positive breast cancer occurs in approximately 25 percent of women with breast cancer.6 About two thirds of women diagnosed with breast cancer have hormone-receptor positive breast cancer.
Excluding skin cancer, breast cancer is the most common form of cancer among women and the second leading cancer killer among women, after lung cancer. The chance of a woman having invasive breast cancer some time during her life is about 1 in 8. The chance of dying from breast cancer is about 1 in 33.5
How is Breast Cancer Treated? Treatment depends on the size and location of the tumor in the breast, the results of lab tests done on the cancer cells and the stage of the disease.7
Breast cancer treatments are local or systemic:
- Local treatments are used to remove, destroy or control the cancer cells in a specific area, such as the breast. Surgery and radiation treatment are local treatments.8
- Systemic treatments are used to destroy or control cancer cells all over the body. Chemotherapy, hormone therapy, and targeted biologic therapy are systemic treatments. A patient may have just one form of treatment or a combination, depending on her needs.9
1 American Cancer Society. Cancer Reference Information: What is Cancer?
2 American Cancer Society. Cancer Reference Information: What is Breast Cancer?
3 BreastCancer.org. How Herceptin Works.
4 American Cancer Society. Cancer Reference Information: What Are the Risk Factors for Breast Cancer?
5 American Cancer Society. How Many Women Get Breast Cancer?
6 BreastCancer.org. Will Herceptin Work for You?
7 National Breast Cancer Foundation. Signs and Symptoms.
8 BreastCancer.org. Local Treatment.
9 BreastCancer.org. Systemic Treatment: The Whole Body.