Risk Factors of Breast Cancer

A risk factor is anything that affects your chance of getting a disease, such as breast cancer. However, having a risk factor, or even several, does not mean that you will get the disease. Most women who have one or more breast cancer risk factors never develop the disease, while many women with breast cancer have no apparent risk factors. Even when a woman with risk factors develops breast cancer, it is hard to know just how much these factors may have contributed to her cancer.

General risk factors:
1. Gender
-Simply being a woman is a main risk factor for the development of breast cancer.
- Women’s breast cells are constantly exposed to the growth-promoting effects of the female hormones estrogen and progesterone, which increases the chances of getting breast cancer.

2. Aging
-The risk of getting breast cancer increases as you age

3. Genetic risk factors
-About 5-10% of breast cancer cases are thought to be hereditary, resulting from gene mutation.
• BRCA 1 and BRCA 2
These are the most common inherited mutations. In normal cells, these genes help to prevent cancer by making proteins that help keep the cells from growing abnormally. When a mutated copy of this gene is inherited, there is increased chances (about 80%)of getting breast cancer and ovarian cancer.
• Changes in other genes
o ATM: The ATM gene normally helps repair damaged DNA. Certain families with a high rate of breast cancer have been found to have mutations of this gene.
o CHEK2: Increases breast cancer risk about twofold when it is mutated. In women who carry the CHEK2 mutation and have a strong family history of breast cancer, the risk is greatly increased.
o p53: Inherited mutations of the p53 tumor suppressor gene can also increase the risk of developing breast cancer, as well as several other cancers such as leukemia, brain tumors, and sarcomas (cancer of bones or connective tissue).
o PTEN: The PTEN gene normally helps regulate cell growth. Inherited mutations in this gene cause Cowden syndrome, a rare disorder in which people are at increased risk for both benign and malignant breast tumors, as well as growths in the digestive tract, thyroid, uterus, and ovaries.

4. Family history of breast cancer
• Breast cancer risk is higher among women whose close blood relatives have this disease.
• Having one first-degree relative (mother, sister, or daughter) with breast cancer approximately doubles a woman's risk. Having 2 first-degree relatives increases
• About 20% to 30% of women with breast cancer have a family member with this disease. (It's important to note this means that 70% to 80% of women who get breast cancer do not have a family history of this disease.)

5. Race and ethnicity
• White women are slightly more likely to develop breast cancer than are African-American women.
• African-American women are more likely to die of this cancer.
• African-American women tend to have more aggressive tumors, although why this is the case is not known
• Asian, Hispanic, and Native-American women have a lower risk of developing and dying from breast cancer.

6. Personal History of Breast Cancer
• A woman with cancer in one breast has a 3- to 4-fold increased risk of developing a new cancer in the other breast or in another part of the same breast. This is different from a recurrence (return) of the first cancer.

7. Dense breast tissue
• Women with denser breast tissue (as seen on a mammogram) have more glandular tissue and less fatty tissue, and have a higher risk of breast cancer.
• Dense breast tissue can also make it harder for doctors to spot problems on mammograms.

8. Certain benign breast conditions
• Women diagnosed with certain benign breast conditions may have an increased risk of breast cancer.
o Non-proliferative lesions
o Proliferative lesions without atypia
o Proliferative lesions with atypia

9. Menstrual periods
• Women who have had more menstrual cycles because they started menstruating at an early age (before age 12) and/or went through menopause at a later age (after age 55) have a slightly higher risk of breast cancer.
• This may be related to a higher lifetime exposure to the hormones estrogen and progesterone.

10. Previous chest radiation
• had radiation therapy to the chest area as treatment for another cancer, increased risk for breast cancer

Lifestyle-related factors and breast cancer risks:
1. Not having children, or having them later in life
• Women who have had no children or who had their first child after age 30 have a slightly higher breast cancer risk.
• Having many pregnancies and becoming pregnant at an early age reduces breast cancer risk.
• Pregnancy reduces a woman's total number of lifetime menstrual cycles, which may be the reason for this effect.

2. Recent oral contraceptive use
• Studies have found that women using oral contraceptives (birth control pills) have a slightly greater risk of breast cancer than women who have never used them, but this risk seems to decline once their use is stopped.

3. Using post-menopausal hormone therapy
• Post-menopausal hormone therapy (PHT), (hormone replacement therapy (HRT)), has been used for many years to help relieve symptoms of menopause and to help prevent osteoporosis (thinning of the bones).
• 2 main types of PHT:
 For women who still have a uterus (womb), doctors generally prescribe estrogen and progesterone (known as combined PHT). Because estrogen alone can increase the risk of cancer of the uterus, progesterone is added to help prevent this.
 For women who no longer have a uterus (those who've had a hysterectomy), estrogen alone can be prescribed. This is commonly known as estrogen replacement therapy (ERT).
• Combined PHT: Long-term use (several years or more) of combined post-menopausal hormone therapy increases the risk of breast cancer and may also increase the chances of dying of breast cancer. Large studies have found that there is an increased risk of breast cancer related to the use of combined PHT. It also increases the likelihood that the cancer may be found at a more advanced stage, possibly because it reduces the effectiveness of mammograms.
The increased risk from combined PHT appears to apply only to current and recent users. A woman's breast cancer risk seems to return to that of the general population within 5 years of stopping combined PHT.
• ERT: The use of estrogen alone does not appear to increase the risk of developing breast cancer significantly, if at all. But when used long term (for more than 10 years), ERT has been found to increase the risk of ovarian and breast cancer in some studies.
At this time there appear to be few strong reasons to use post-menopausal hormone therapy (combined PHT or ERT), other than possibly for the short-term relief of menopausal symptoms. The decision to use PHT should be made by a woman and her doctor after weighing the possible risks and benefits (including the severity of her menopausal symptoms), and considering her other risk factors for heart disease, breast cancer, and osteoporosis. If a woman and her doctor decide to try PHT for symptoms of menopause, it is usually best to use it at the lowest dose that works for her and for as short a time as possible.

4. Not breast-feeding
• Some studies suggest that breast-feeding may slightly lower breast cancer risk, especially if breast-feeding is continued for 1½ to 2 years. But this has been a difficult area to study, especially in countries such as the United States, where breast-feeding for this long is uncommon.
• The explanation for this possible effect may be that breast-feeding reduces a woman's total number of lifetime menstrual cycles (similar to starting menstrual periods at a later age or going through early menopause).

5. Alcohol
• Use of alcohol is clearly linked to an increased risk of developing breast cancer. The risk increases with the amount of alcohol consumed.
• Compared with non-drinkers, women who consume 1 alcoholic drink a day have a very small increase in risk. Those who have 2 to 5 drinks daily have about 1½ times the risk of women who drink no alcohol.

6. Being overweight or obese
• Being overweight or obese has been found to increase breast cancer risk, especially for women after menopause.
• Before menopause, your ovaries produce most of your oestrogen and fat tissues produces a small amount of estrogen. After menopause (when the ovaries stop making estrogen), most of a woman's estrogen comes from fat tissue. Having more fat tissue after menopause can increase your estrogen levels and thereby increase your likelihood of developing breast cancer.
The connection between weight and breast cancer risk is complex. For example, the risk appears to be increased for women who gained weight as an adult but may not be increased among those who have been overweight since childhood. Also, excess fat in the waist area may affect risk more than the same amount of fat in the hips and thighs. Researchers believe that fat cells in various parts of the body have subtle differences that may explain this.

7. Lack of physical activity
• Evidence is growing that physical activity in the form of exercise reduces breast cancer risk.

There are other unproven, controversial and uncertain effect on breast cancer risk. For full text, see http://www.cancer.org/docroot/CRI/content/CRI_2_4_2X_What_are_the_risk_factors_for_breast_cancer_5.asp