Are there drugs available that can reduce the risk of breast cancer for women at high risk?

Research has shown that certain drugs may reduce the risk of developing hereditary breast cancer. Preventive medications for breast cancer are the subject of much ongoing research. Depending on where you live in Canada, access to chemoprevention drugs will vary. Consult your doctor for more information.

Chemoprevention should not be confused with chemotherapy, which is used to treat cancer. Although these chemopreventive drugs have side effects, they are not as severe as those associated with chemotherapy, such as hair loss.


Tamoxifen is a pill that you take every day for five years. Tamoxifen blocks the effects of estrogen, which reduces the risk of developing breast cancer.

Who can take tamoxifen?

Tamoxifen is the most commonly used drug to reduce the risk of breast cancer in high-risk women 35 years of age or older. You can take tamoxifen whether you have gone through menopause or not.

What are the side effects of tamoxifen?

  • hot flashes and night sweats
  • vaginal changes such as dryness, discharge and itching
  • rare, but serious, problems include uterine cancer, blood clots, stroke, and cataracts

Though taking this medication may reduce your risk of developing breast cancer, it will not totally eliminate it. It is not as effective as risk-reducing surgery but it is an option for some women to consider. If you choose this option you will still need to undergo routine breast screening.

Other drugs which may be effective at reducing breast cancer risk in high-risk women include raloxifene and exemestane. Neither has yet been approved for this use in Canada, though they may be approved for this use in other countries.

Medication can be an alternative to having a risk-reducing mastectomy. Remember the best choice for lowering your cancer risk is based on the issues most important for you.


Diet and Excercise

Researchers continue to study how diet and exercise may affect breast cancer risk. Research has shown that the following recommendations can reduce breast cancer risk in the general population of women. Although their effect on hereditary breast cancer risk is not known, these recommendations are likely to help with your overall health.

  • Exercise (e.g. walk, bike, run, or swim) for 20-30 minutes on most days of the week.
  • Limit weight gain in adult years to less than 5 kg (11 pounds).
  • Try not to have more than one drink containing alcohol each day. 1 drink = 100 ml(4 oz) of wine, 250 ml(8 oz) of beer, or 25 ml(1 oz) of spirits
  • Eat a well-balanced diet with at least 7-8 servings of vegetables and fruits each day. 1 serving = 1 medium-sized piece or 135 ml (1/2 cup) of fruit or vegetables. Choose a variety of dark green and orange fruits and vegetables.