Breast Cancer: Part 2

The following factors are linked to a decreased risk of breast cancer:

Selective Estrogen Receptor Modulators (SERMs)

SERMs are drugs that act like estrogen on some tissues in the body such as bones, but block the effect of estrogen on other tissues. Tamoxifen is a SERM that blocks the effect of estrogen on breast cancer cells. A large study has shown that tamoxifen lowers the risk of getting breast cancer in women who have an increased risk of getting breast cancer. However, tamoxifen may also increase the risk of endometrial cancer, stroke, and blood clots in veins and in the lungs. Anyone concerned that they may be at an increased risk of developing breast cancer should talk with their doctor about whether to take tamoxifen to prevent breast cancer. It is important to consider both the benefits and risks of taking tamoxifen.

Raloxifene is another SERM that is being studied for the prevention of breast cancer. A study of postmenopausal women with osteoporosis has shown that raloxifene lowered the risk of breast cancer for women at both high risk and low risk of developing the disease. It is not known if women who do not have osteoporosis would benefit in the same way. Like tamoxifen, raloxifene may increase the risk of blood clots in veins and in the lungs, but does not appear to increase the risk of endometrial cancer.

Aromatase Inhibitors

In some who is postmenopausal, aromatase inhibitors decrease the body’s estrogen and lower the risk of breast cancer. After menopause, most of a woman’s estrogen is made outside the ovaries from androgen, another hormone. Aromatase inhibitors stop an enzyme called aromatase from turning androgen into estrogen. Possible harms from taking aromatase inhibitors include decreased bone density and effects on brain function (such as talking, learning, and memory).

Prophylactic Mastectomy

The removal of both breasts may reduce the risk of breast cancer in women with a family history of breast cancer. Before making the decision to have prophylactic mastectomy, it is important to undergo cancer risk assessment and counseling, and to carefully consider all the treatment options. In some women, prophylactic mastectomy may cause anxiety, depression, and concerns about body image.

Prophylactic oophorectomy

The removal of ovaries (one or both), decreases the amount of estrogen made by the body and decreases the woman’s breast cancer risk. Also, drugs may be taken to decrease the amount of estrogen made by the ovaries. The sudden drop in estrogen may cause the following symptoms of menopause to occur:

  • Hot flashes.
  • Trouble sleeping.
  • Anxiety.
  • Depression.
  • Lack of interest in sex.
  • Vaginal dryness.
  • Loss of bone density.


Exercising 4 or more hours a week may decrease hormone levels and help lower breast cancer risk. The effect of exercise on breast cancer risk is stronger in younger women of normal or low weight. Care should be taken to exercise safely, as physical activity carries the risk of injury to bones and muscles.

The effect of the following factors on the risk of breast cancer is not known:


Studies have not proven a link between abortion and breast cancer.


Studies have not proven that certain environmental exposures (such as chemicals, metals, dust, and pollution) increase the risk of breast cancer.


Diet is being studied as a risk factor for breast cancer. It is not proven that a diet low in fat or high in fruits and vegetables will prevent breast cancer. Studies have shown, however, that eating a diet rich in beta-carotene may decrease the risk of breast cancer. A diet rich in beta-carotene, folate, and vitamins A and C may reverse the higher risk of breast cancer linked to alcohol use.


Studies have not found that taking statins (cholesterol-lowering drugs) affects the risk of breast cancer.

To find out more visit the National Cancer Institute.

Source: National Cancer Institute

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