What causes breast cancer?
The exact cause or causes of breast cancer remain unknown. Yet scientists have identified a number of risk factors that increase a person's chance of getting this disease. Certain risk factors, such as age, are beyond our control; whereas others, like drinking habits, can be modified. About 50% of women who develop breast cancer have no risk factors other than age and sex. Sex is the biggest risk because breast cancer occurs mostly in women. Age is another critical factor. Breast
cancer may occur at any age, though the risk of breast cancer increases with age. The average woman at age 30 years has 1 chance in 280 of developing breast cancer in the next 10 years. This chance increases to 1 in 70 for a woman aged 40 years, and to 1 in 40 at age 50 years. A 60-year-old woman has a 1 in 30 chance of developing breast cancer in the next 10 years.
Genetic causes - Family history has long been known to be a risk factor for breast cancer. The risk is highest if the affected relative developed breast cancer at a young age or if she is a close relative such as a mother, sister, daughter, or aunt. There is great interest in genes linked to breast cancer. BRCA1 is an abnormal gene that, when inherited, markedly increases the risk of breast cancer to a lifetime risk of almost 85%. Women with this abnormal gene also have an increased likelihood of developing ovarian cancer. Women who have the BRCA1 gene tend to develop breast cancer at an early age. A second abnormal gene, BRCA2, increases the risk of developing breast cancer but not ovarian cancer. Testing for these genes is expensive and frequently not covered by insurance. In addition, women who test positive may have trouble getting or keeping health insurance. The issues around testing are complicated, and women who are interested in testing should discuss this with their health care providers.
Hormonal causes - Hormonal influences play a role in the development of breast cancer. Women who start their periods at an early age or experience a late menopause have a higher risk of developing breast cancer. Conversely, being older at your first menstrual period and early menopause tend to protect one from breast cancer. Having a child before age 30 years may provide some protection, and having no children may increase your risk for developing breast cancer. Oral contraceptives have not been shown to increase or decrease a woman's the lifetime risk of breast cancer. Studies about the effects of hormone replacement (HRT) after menopause have had conflicting results. Some studies suggest that the risk of breast cancer is increased in women who take hormones after menopause for prolonged periods. Long-term hormone replacement is no longer routinely recommended because of its association with higher rates of heart attack and stroke.
Dietary causes - Breast cancer seems to occur more frequently in countries with high dietary intake of fat. This link is thought to be an environmental influence rather than genetic. For example, Japanese women, at low risk for breast cancer while in Japan, increase their risk of developing breast cancer after coming to the United States. Several studies comparing groups of women with high- and low-fat diets, however, have failed to show a difference in breast cancer rates.
Benign breast disease - Fibrocystic breast changes are very common. Fibrocystic breasts are lumpy with some thickened tissue and are frequently associated with breast discomfort, especially right before your menstrual period. This condition does not lead to breast cancer. However, certain types of benign breast changes, such as those diagnosed on biopsy as proliferative or hyperplastic, do predispose women to the later development of breast cancer.
Environmental causes - Radiation treatment seems to increase the likelihood of developing breast cancer but only after a long delay. For example, women who received radiation therapy to the upper body for treatment of Hodgkin disease before age 15 years have a significantly higher rate of breast cancer than the general population.
Alcohol use - The risk of breast cancer is increased among women who drink. Women who consume one alcoholic beverage a day have a slightly increased risk of breast cancer. By contrast, breast cancer risk is nearly doubled in women who have more than three drinks daily. Although the basis for this association is unknown, there is a recognized relationship between the consumption of more than two drinks a day and an increased level of estrogen in the blood.
Radiation exposure - A significantly increased risk of breast cancer has been found in women who received radiation therapy in the chest area during childhood or young adulthood. Because of former medical practices (for example, the repeated use of fluoroscopic x-rays to check the lungs for tuberculosis), women over 45 generally have more exposure to radiation than younger women. In addition, an increased risk of breast cancer has been seen in women who were exposed to atomic bomb radiation at Hiroshima and Nagasaki, Japan.
More information on breast cancer
What is breast cancer? - Breast cancer is cancer of breast tissue. Breast cancer starts in the cells of the breast. Breast tissue covers a larger area than just the breast.
What types of breast cancer are there? - Breast cancer is a type of uncontrolled growth of abnormal cells that can develop in one of several different areas of the breast.
What're the risk factors for breast cancer? - Risk factors for breast cancer include age, geographical variation, reproductive factors, inherited risk, previous breast disease.
What're the symptoms of breast cancer? - Symptoms of breast cancer include breast lump, breast discharge, nipple inversion, or changes in the skin overlying the breast.
How is breast cancer diagnosed? - The mainstay of breast cancer diagnosis is the triad of clinical history, physical examination and imaging (mammography or ultrasound).
What're the stages of breast cancer? - The stages of breast cancer depends on its size and the extent to which it has spread to other parts of the body.
What causes breast cancer? - The exact cause or causes of breast cancer remain unknown. Hormonal influences play a role in the development of breast cancer.
What're the treatments for breast cancer? - Treatment for breast cancer begins with a decision about the type of surgery. Breast implants is used for breast reconstruction.
What're the side effects of breast cancer treatment? - The type and extent of breast cancer treatment side effects vary depending on the particular treatment involved, its duration, and its dose.
How is breast cancer treated with surgery? - Surgery is the mainstay of therapy for breast cancer. A breast biopsy is the removal of breast tissue for examination by a pathologist.
What's the chemotherapy for breast care? - Chemotherapy is the use of anti-cancer drugs to treat cancerous cells. Chemotherapy involves being given a combination of anti-cancer medicines.
What's the radiation therapy for breast cancer? - Radiation therapy is often used to destroy any remaining breast cancer cells in the breast, chest wall, or axilla (underarm) area after surgery.
What's the hormone therapy for breast cancer? - Most breast cancer is sensitive to the female hormone oestrogen. Megestrol acetate is used for hormone treatment of advanced breast cancer.
What breast cancer medications are available? - Medications to treat breast cancer include selective estrogen-receptor modulators, aromatase inhibitors, biologic response modifiers.
Can breast cancer be prevented? - There is no known way to prevent breast cancer. But several preventive measures can be take to reduce risk of breast cancer.