Breast Cancer Resources Center

The best approach is to avoid as many risk factors as possible while increasing protective factors.

Doctors and scientists do not know why one person gets cancer and another one does not. Review the following "proven" risk factors that may increase the chance of getting breast cancer:

Estrogen: Being exposed to estrogen over a long time may increase the risk. This increased exposure occurs in the following ways:

1. Early menstruation: Beginning to have menstrual periods at age 11 or younger increases the number of years the breast tissue is exposed to estrogen.

2. Late menopause: The more years a woman menstruates, the longer her breast tissue is exposed to estrogen.

3. Late pregnancy or never being pregnant: Because estrogen levels are lower during pregnancy, the tissue is exposed to more estrogen in women who become pregnant for the first time after age 35 or who never become pregnant.

Other risk factors include:

1. Hormone replacement therapy/Hormone therapy: Therapies given to women who have had their ovaries removed or who have had a hysterectomy

2. Exposure to Radiation: Radiation to the chest for the treatment of cancers starting 10 years after treatment and lasting for a lifetime. The risk depends on the dose of radiation and the age at which it is given. The risk is highest if radiation treatment was used during puberty. Radiation therapy to treat cancer in one breast does not appear to increase the risk of developing cancer in the other breast.

3. Obesity: Increases the risk in post-menopausal women who have not used hormone replacement therapy.

4. Alcohol: Drinking alcohol increases the risk. Risk rises as the amount of alcohol consumed rises.

5. Inherited risk

Protective factors that may decrease the risk include:

1. Exercise: Exercising four or more hours a week may decrease hormone levels and help lower breast cancer risk. This effect is greatest in pre-menopausal women of normal or low weight.

2. The risk appears to be lower if a woman has her first full-term pregnancy before she is 20 years old.

3. Breast-feeding: Because estrogen levels are lower during breastfeeding, a woman may decrease her risk.

4. Ovarian ablation: Estrogen is reduced when one or both ovaries are removed and can decrease the risk.

5. Late menstruation: At age 14 or older decreases the chances of breast cancer.

6. Early menopause: The fewer years a woman menstruates, the shorter the time her breast tissue is exposed to estrogen.

7. Tamoxifen: Lowers the risk in women who are at high risk for the disease. The effect last for several years after drug treatment is stopped.

8. Raloxifene: Helps prevent breast cancer in post-menopausal women with osteoporosis.

9. Aromatase inhibitors: Lowers the risk of new breast cancers in post-menopausal women with a history of the disease.

10. Prophylactic mastectomy: Some women with high risk may choose to have both breasts removed when there are no signs of cancer. The risk of is lowered in these women. It is very important to have a cancer risk assessment and counseling about all options for possible prevention before making this decision.

11. Prophylactic oophorectomy: Women who have a high risk may choose to have a prophylactic oophorectomy (removal of both ovaries when there are no signs of disease) to decrease the amount of estrogen made by the body and lower the risk. It is very important to have a cancer risk assessment and counseling before making this decision.

12. Fenretinide: At type of vitamin A called retinoid that may lower the risk when given to pre-menopausal women who have a history of the disease.

The following have been proven NOT to be risk factors or their effects are not known:

1. Abortion

2. Oral Contraceptives

3. Progestin-only contraceptives that are injected or implanted

4. Environment: Studies have not proven that being exposed to certain substances in the environment such as chemicals, metals, dust and pollution) increases the risk.

5. It is not proven that a diet low in fat or high in fruits and vegetables will prevent breast cancer.

6. It has not been proven that either active cigarette smoking or passive smoking (inhaling secondhand smoke) increases the risk of developing the disease.

There are new studies going on continuously to find more ways to prevent breast cancer. These studies include:

• The effects of exercise

• The effects of quitting smoking or taking certain medicines, vitamins, minerals or food supplements

Source: National Cancer Institute

© 2007 Connie Limon

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