Risk Reducing Medication

Breast Cancer Risk Reducing Medication

Risk-reducing medication may be considered for use by women who have been assessed as being at increased risk of breast cancer, based on family history. This is less than 5% of women.

The main medications that women consider are medications known as Selective Estrogen Receptor Modulators (SERMs). They work by blocking the hormone, estrogen, from binding on to breast cells. They are Tamoxifen (which can work in pre and post-menopausal women), and Raloxifene which has only been tested in postmenopausal women.

There is another type of medication known as Aromatase Inhibitors (AIs) such as anastrazole and exemestane, that may be considered for women who are post-menopausal. These reduce the production of estrogen (in tissues other than in the ovaries) but they only work in women who are post-menopausal.
The decision to take risk reducing medication should only be made after a discussion about all relevant management options, including screening, and risk-reducing surgery (if appropriate), taking into account the woman’s individual risk category, age, stage of life and preferences.

You and your doctor will be able to review all the relevant factors to make an informed decision as to whether risk reducing medication is the way forward for you.

More information can be found at Cancer Australia.

Benefits of Risk Reducing Medication
Both Tamoxifen and Raloxifene reduce the risk of hormone receptor positive invasive breast cancer in women if taken as a daily tablet for 5 years. Whilst no one can predict what type of breast cancer a woman will develop, the majority of breast cancers women develop are hormone receptor positive breast cancers. Even though these medications reduce the risk of developing breast cancer (and of needing treatment), we do not know that using them as a risk-reducing medication will actually lead to a longer life.

If a woman has not entered menopause (pre-menopausal), then Tamoxifen is the only medication that is relevant to consider.

If a woman is in menopause (post-menopausal), then the options also include Raloxifene, or another class of medication, the Aromatase inhibitors (AIs), such as Anastrazole or Exemestane.

How effective are these medications?
The amount of risk reduction varies from one woman to another. This is because it depends on how much risk a woman starts with. Overall Tamoxifen seems to reduce the risk by about a third and the effect of the medication works for at least 20 years. The STAR trial showed that Tamoxifen was slightly more effective than Raloxifene in preventing breast cancer for post-menopausal women (but was not tested in pre-menopausal women).

On the other hand, Raloxifene has slightly different side effects (see below), so this needs to be weighed up with a breast specialist, if you are considering one of these medications. The AI medications have not been directly compared to Tamoxifen or Raloxifene. However, when the AI medications were compared to placebo (dummy pills) in trials, a daily tablet of the AI medications reduced risk by about half . It is still difficult to know if this means that their effect is more than the Tamoxifen/Raloxifene. The reduction in risk from the AI medications also depends on how high the breast cancer risk was to start with, so it is good to talk to a doctor who can provide more detailed information to help you decide.

Risks of Risk Reducing Medication
These lists are not exhaustive but are a general guide for each of the medications described.

Tamoxifen
As with any medications, there are risks and possible side-effects. Tamoxifen should not be taken if a woman is:

  • Pregnant or breast-feeding
  • Using the oral contraceptive (Tamoxifen can make this less effective)
  • A smoker (this increases blood clot risk)
  • Has had a past history of blood clots in the legs, lungs or a stroke or mini-stroke
  • Is using hormone replacement therapy

If a woman is planning to become pregnant in the next few (less than 5) years, then it may be better to think about taking the medication after having had children. This is because we do not know if taking the medication for less than 5 years will have a protective effect on breast risk.

You should discuss with your doctor if you are using any existing medications and whether these will interact with Tamoxifen.

Common side effects
The most common side effects of Tamoxifen are hot flushes and sweats, especially at night. Sometimes these lessen over the first few months. Possible gynaecological symptoms include vaginal discharge and sometimes, itch, and menstrual irregularities. Each woman’s experience is different and we cannot predict if a woman will have any of these problems.

Less common side effects
Tamoxifen can increase the risk of endometrial (womb) cancer in post-menopausal women (not pre-menopausal women) from about 1 in 1000 women per 5 years to 4 in 1000 women per 5 years of use. This appears to be only for the time the medication is taken. This risk does not appear to apply to Raloxifene and the AI medications.

There is a small increase in risk of blood clots (deep vein blood clots in the legs which can go to the lungs) in pre and post-menopausal women with Tamoxifen. This is about 4 per 1000 women over 5 years of Tamoxifen. The risk may be more in women who smoke or have a past history of blood clots. Although the risk of developing blood clots is low (particularly in premenopausal women), this is a serious and potentially life-threatening side effect. The risk of these events returns to normal when Tamoxifen is stopped.

Women may need to stop taking Tamoxifen prior to any surgery. This should be discussed with a healthcare team. It should also be stopped at least three months before trying to start a family.

Raloxifene
Raloxifene should not be used in premenopausal women as it has only been trialled in postmenopausal women.

In postmenopausal women, it should be avoided if a woman:

  • Is smoker (this increases blood clot risk)
  • Has had blood clots in the legs, lungs or a stroke or mini-stroke
  • Is using hormone replacement therapy

Common side effects
The most common side effects of Raloxifene are hot flushes and sweats, especially at night. Sometimes these lessen over the first few months. Possible gynaecological symptoms include vaginal discharge and sometimes itch, and menstrual irregularities. Each woman’s experience is different and we cannot predict who will have these symptoms.

Less common side effects
There is a small increase in risk of blood clots (deep vein blood clots in the legs which can go to the lungs) in pre and post-menopausal women with Raloxifene. This is about 3 per 1000 women per 5 years of Raloxifene so it is a bit less than with Tamoxifen. The risk may be more in women who smoke or have a past history of blood clots. Although the risk of developing blood clots is relatively low, this is a serious and potentially life-threatening side effect. The extra risk of these events returns to normal when Raloxifene is stopped.

Women may need to stop taking Raloxifene prior to any surgery. This should be discussed with your healthcare team.

Aromatase inhibitor (AI) medications such as anastrazole and exemestane
These medications should be avoided if a woman could still be pre-menopausal as they will not be effective. Menopausal status needs to be checked by a doctor before these are considered.

AIs should also be avoided if a woman:

  • Is taking hormone replacement (as they will not be effective)
  • Has osteoporosis (as they increase the risk of bone thinning)

Common side effects
The most common side effects of these medications, as with the SERMS, are hot flushes and sweats, especially at night. Sometimes these lessen over the first few months. Possible gynaecological symptoms include vaginal dryness. Each woman’s experience is different and we cannot predict who will have these symptoms, but they do appear to stop when the medications are stopped.

Other side effects can include joint aches which vary in severity from one person to another.

Less common side effects
The risk of osteoporosis is increased so bone density needs to be monitored while taking these medications by bone density scans (X-rays). Women are advised to take calcium and Vitamin D while on these medications. In contrast, the SERM medications are likely to help with protecting bone density in post-menopausal women.

Ovarian Cancer Risk Reducing Medication

Oral contraceptive pills reduce ovarian cancer risk by about a factor of a half, but as they do not eliminate the risk (and may increase breast risk to a slight degree) they are not generally used as a ovarian cancer risk-reducing medication.

Having your tubes tied or removed also reduces ovarian risk but the best way to reduce an ovarian cancer risk is by having your ovaries and Fallopian tubes surgically removed. This is advised only for a small percentage of women who have a high ovarian risk, and generally after age 40 years (refer to the risk management section of the Pink Hope website.

Click here to refer to the FAQs on Risk Reducing Medication.

You may also be interested in