What causes breast cancer?

Certain changes in DNA can cause normal breast cells to become cancer. DNA is the chemical in each of our cells that makes up our genes -- the instructions for how our cells work. Some inherited DNA changes (mutations) can increase the risk for developing cancer and cause the cancers that run in some families. For instance, BRCA1 and BRCA2 are tumor suppressor genes -- they keep cancer tumors from forming. When they are changed (mutated), they no longer cause cells to die at the right time, and cancer is more likely to develop.
But most breast cancer DNA changes happen in single breast cells during a woman's life rather than having been inherited. So far, the causes of most of the DNA mutations that could lead to breast cancer are not known.

Risk Factors

While we do not yet know exactly what causes breast cancer, we do know that certain risk factors are linked to the disease. A risk factor is something that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, such as smoking, drinking, and diet are linked to things a person does. Others, like a person's age, race, or family history, can't be changed.
But risk factors don't tell us everything. Having a risk factor, or even several, doesn't mean that a woman will get breast cancer. Some women who have one or more risk factors never get the disease. And most women who do get breast cancer don't have any risk factors. Some risk factors have a greater impact than others, and your risk for breast cancer can change over time, due to factors such as aging or lifestyle.
Although many risk factors may increase your chance of having breast cancer, it is not yet known just how some of these risk factors cause cells to become cancer. Hormones seem to play a role in many cases of breast cancer, but just how this happens is not fully understood.

Genetic Causes

Family history has long been known to be a risk factor for breast cancer. Both maternal and paternal relatives are important. The risk is highest if the affected relative developed breast cancer at a young age, had cancer in both breasts, or if she is a close relative. First-degree relatives, (mother, sister, daughter) are most important in estimating risk. Several second-degree relatives (grandmother, aunt) with breast cancer may also increase risk. Breast cancer in a male increases the risk for all his close female relatives. Having relatives with both breast and ovarian cancer also increases a woman's risk of developing breast cancer.

Hormonal Causes

· Women who start their periods at an early age (11 or younger) or experience a late menopause Conversely, being older at the time of the 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 the risk for developing breast cancer.

· Oral contraceptives have not been shown to definitively increase or decrease a woman's lifetime risk of breast cancer.

· A large study conducted by the women health initiative showed an increased risk of breast cancer in postmenopausal women who were on a combination of estrogen and progesterone for several years. Therefore, women who are considering hormone therapy for menopausal symptoms need to discuss the risk versus the benefit with their health-care providers.

Lifestyle and Dietary Causes

Breast cancer seems to occur more frequently in countries with high dietary intake of fat, and being overweight obese is a known risk factor for breast cancer, particularly in postmenopausal women.

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.

The use of alcohol is also an established risk factor for the development of breast cancer. The risk increases with the amount of alcohol consumed. Women who consume two to five alcoholic beverages per day have a risk about one and a half times that of nondrinkers for the development of breast cancer. Consumption of one alcoholic drink per day results in a slightly elevated risk.

Studies are also showing that regular exercise may actually reduce a woman's risk of developing breast cancer. Studies have not definitively established how much activity is needed for a significant reduction in risk. One study from the Women's Health Initiative (WHI) showed that as little as one and a quarter to two and a half hours per week of brisk walking reduced a woman's breast cancer risk by 18%.

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 the menstrual period. This condition does not lead to breast cancer.
However, certain other types of benign breast changes, such as those diagnosed on biopsy as proliferative or hyper plastic, do predispose women to the later development of breast cancer.

Environmental Causes

Radiation treatment increases 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’s disease before 30 years of age have a significantly higher rate of breast cancer than the general population.

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Friday, July 8, 2011

Causes of Breast Cancer

What causes breast cancer?

Risk Factors

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