What is Breast Cancer | Key Statistics | Risk Factors | Risk Reduction | Survival Rates

A risk factor is any underlying reason that increases a person's chance of getting a disease. However, having one or more risk factors does not necessarily mean that a person will develop the disease. The majority of women who develop breast cancer have no apparent risk factors, while some women with one or more risk factors never develop the disease.

The following are some of the risk factors for breast cancer:

Age: The risk of developing breast cancer increases as a woman gets older. Approximately one out of eight breast cancers are diagnosed in women under the age of 45, while, two out of three are in women 55 and older.

Race: White women have a slightly higher incidence of breast cancer than African-American women, but African-American women are more likely to die of the disease. The primary reason for the difference in mortality rates is later diagnosis in African-American women, when the disease is more advanced and harder to treat. However, there is some recent evidence that suggests African-American women develop more aggressive forms of breast cancer. The risk of developing breast cancer is lower in Asian, Hispanic, and Native American women.

Family History of Breast Cancer: The risk of breast cancer is greater in women whose close blood relatives, on the side of the mother or the father, have a history of the disease. A woman's risk of developing breast cancer is approximately doubled if her mother, sister, or daughter has a history of breast cancer. The risk is nearly five times as great if there are two previous cases of breast cancer in the mother, sister, or daughter. Approximately 20% to 30% of women diagnosed with breast cancer have a family member with the disease.

Personal History of Breast Cancer: If a woman has developed cancer in one breast, her risk of developing a new cancer in the other breast or in a different section of the same breast is three to four times higher than in a woman with no previous history of breast cancer.

Genetic Risk Factors: Approximately 5% to 10% of all breast cancer cases are due to inherited genetic mutations. There are several inherited genetic mutations that have been associated with an increased risk of developing breast cancer:

BRCA1 (breast cancer gene 1) and BRCA2 (breast cancer gene 2): In their non-mutated form, these genes function as tumor suppressors, producing proteins meant to prevent abnormal cell growth. Mutated BRAC1 or BRCA2 genes are no longer able to function as tumor suppressors, so breast cancer is more likely to develop. The estimated lifetime risk of women with inherited mutated BRCA1 or BRCA2 of developing breast cancer is up to 80%. Women with these mutated genes also have a higher risk of developing ovarian cancer.

p53 tumor suppressor: The job of P53 is to prevent cells from growing abnormally and forming tumors. Inherited genetic mutations of this gene may increase the risk of developing breast cancer, as well as leukemia, brain tumors, and cancers of the bone and connective tissue. Almost 50% of all human cancer cells contain a P53 mutation. These cancers are more aggressive and more often fatal.
In addition, a rare condition known as Li-Fraumeni syndrome may develop if a person inherits only one functional copy of the p53 gene from their parents. This syndrome, named after the two researchers who first identified it, may also result in an increased risk of developing breast cancer.

Ataxia telangiectasia mutated (ATM): This is a recessive gene that increases the risk for people to develop multiple forms of cancer, including primary breast cancer. Normally, the ATM gene is responsible for detecting and repairing DNA damage or destroying damaged cells that can't be repaired. This process is interrupted in mutated genes, allowing cancer cells to develop. An estimated 1% of Americans (more than 2 million people) carry at least one copy of the defective form of the gene.

CHEK2: It is believed that a normal CHEK2 gene shuts down cells in a safe and controlled way upon detection of DNA damage. This prevents the cell from passing on faulty DNA, and allows time for repair mechanisms to be engaged. In the mutated version of CHEK-2, the gene is unable to initiate shutdown and faults in other genes are more likely to evade the body's repair processes. This may potentially lead to tumor development and has been associated with an increased risk of breast cancer.
History of Abnormal Breast Condition: There are some benign breast conditions that may increase a woman's chance of eventually developing breast cancer. These conditions are usually diagnosed through a breast biopsy and include:

Fibroadenoma with complex features: Fibroadenomas are composed of both glandular and connective tissue and appear in the breast as marble-like lumps of varying sizes. A fibroadenoma with complex features is identified through a microscopic examination of tissue and may differ from non-complex fibroadenomas by the presence of calcifications or cystic changes.

Proliferative breast disease, or hyperplasia: This disease is characterized by an overgrowth of cells in the inner lining of the milk glands. If the lining has an extra layer of cells but each of the cells looks ordinary, the condition is called proliferative disease without atypia, or hyperplasia without atypia. Women with this condition have a 1.5 to 2.0 times greater risk of developing breast cancer.
If the extra cells are irregular or look odd, the condition is called atypical hyperplasia. Women with a previous diagnosis of atypical hyperplasia have a 4 to 5 times greater risk of developing breast cancer.

Sclerosing adenosis: Sclerosing adenosis is a benign condition where extra tissue grows within the breast lobules. This can cause recurring pain (which may be related to the menstrual cycle) or result in a small, firm lump in the breast. Women with a previous history of this condition have a 1.5 to 2.0 times greater risk of developing breast cancer than other women.

Solitary papilloma: A solitary papilloma is a small, wartlike growth that projects into breast ducts near the nipple. Single (solitary) intraductal papillomas usually affect women nearing menopause and are associated with a 1.5 to 2.0 times greater risk of eventually developing breast cancer.
Childhood Radiation Therapy: A greater chance of developing breast cancer exists for women whose breasts were exposed to radiation as a child or young adult as treatment for another cancer, such as Hodgkin's disease disease or non-Hodgkin lymphoma. Some estimates put this risk as high as 12 times greater, but the risk varies according to the age of the patient at the time of radiation.

Breast Density: Women aged 45 and older with at least 75% dense breast tissue are at an increased risk for developing breast cancer. Dense breasts contain more glandular and connective tissue. Less dense breasts are mainly made up of fat tissue. Every woman has different amounts of the different types of tissue in her breasts.

Diethylstilbestrol (DES): DES was prescribed in the 1940's through the 1960's to lower the risk of miscarriage. Recent studies have shown that women who used DES have a slightly increased risk of developing breast cancer.

Long Menstrual History: Women with early onset of menstruation (before the age of 12) or late onset of menopause (after the age of 55) have a slightly increased risk of developing breast cancer.

Late Childbearing: Women who had their first child after the age of 30 or who have had no children have a slightly increased risk of developing breast cancer. Women with multiple pregnancies and who became pregnant at an early age have a reduced breast cancer risk.

Alcohol Use: Women who consume one alcoholic drink a day have a slightly increased risk of developing breast cancer as compared to nondrinkers. Women who have 2 to 5 drinks a day have about 1.5 times the risk of developing breast cancer as nondrinkers. Alcohol is also known to increase the risk of developing cancers of the mouth, throat, and esophagus.

Hormone Replacement Therapy: Several recently-concluded large studies have shown that there is an increased risk of breast cancer in women using hormone replacement therapy (HRT) that combines estrogen and progesterone; however, women using estrogen therapy (ERT) alone are at no greater risk than normal. Use of ERT alone is limited to women who have had their uterus removed, because, in addition to offsetting the effects of menopause and preventing osteoporosis, estrogen also increases the chance of developing uterine cancer. Progesterone helps to prevent uterine cancer; therefore, combined HRT is usually prescribed for women with intact uteruses.

These recent studies also show that combined HRT also increases the likelihood that the cancer will be found at a more advanced stage and that women who took the combined therapy were also more likely to die of breast cancer than women who didn't.

The risk of HRT appears to apply only to current and recent users, and a woman's breast cancer risk seems to return to that of the general population within 5 years of stopping HRT. The beneficial effects of hormone replacement therapy must be considered when a woman and her physician discuss the use of hormone replacement therapy.

Obesity: Women who are overweight have an increased risk of developing breast cancer, particularly after menopause. This risk is associated with women who became overweight as an adult, but does not seem to be connected to women who have been overweight since childhood. In addition, women with excess fat in the waist are at a higher risk than obese women with the same amount of fat in other areas of the body, such as hips and thighs.

Other Potential Risk or Risk Reduction Factors: There are a number of other factors that have been explored as having the potential to either increase or decrease the risk of breast cancer; however, studies and investigations have not established a definitive relationship with risk. Some other factors include:

Potential Factors to Reduce The Risk of Breast Cancer: Breast feeding: Some studies suggest breast feeding may slightly reduce the risk of breast cancer, particularly if continued for 1.5 to 2 years; however, other studies have failed to demonstrate any relationship between breast feeding and risk reduction.

Potential Factors to Increase The Risk of Breast Cancer: Oral Contraceptive Use: Studies in this area are non-conclusive, but there is some indication that the use of birth control pills may slightly increase the risk of breast cancer. There is no evidence of increased risk 10 years after discontinuing the use of oral contraceptives.

Environmental Pollutants: Although no clear links have been shown between breast cancer and pollution, extensive research is being carried out to determine possible environmental causes of breast cancer.

Other Unproven Risk Factors: There are a number of other factors cited as potential risk factors for breast cancer; however, there is no evidence that can be used to support the validity of an increase in breast cancer. Some of those factors include: the use of antiperspirants; the use of underwear bras; breast implants; spontaneous or induced abortions; smoking; night work; and antibiotics