If you are concerned about your risk of developing breast cancer, it is understandable to look into ways of reducing that risk wherever possible. Lifestyle changes that restrict breast cancer risk are often associated with many other health benefits.
In conjunction with lifestyle factors, it is important to be vigilant about breast cancer detection. Noticing any skin changes or lumps and discussing these with your doctor, in addition to the recommended mammograms or other screening, is an important part of monitoring for breast cancer, especially in women with a higher-than-average risk.
Modifiable risk factors
There is growing evidence that exercise reduces the risk of developing many cancers, including breast cancer. In the Women’s Health Initiative study, 1.25 to 2.5 hours of brisk walking per week reduced a woman’s risk by as much as 18%. Exercise should be of moderate intensity – enough to make you breathe faster without making you breathless. Resistance-based exercise, such as working with weights, has not been shown to have the same protective effects.
Children and breastfeeding
Giving birth before the age of 30 is associated with a reduction in the risk of breast cancer compared to those who do not have children or have their first child after age 30.
Breastfeeding, particularly if for 12 months or longer, can lower breast cancer risk.
Maintaining a healthy weight
Particularly in post-menopausal women, increased fat tissue is associated with a moderate increase in breast cancer risk. Maintaining a healthy weight restricts the amount of oestrogen-producing fat tissue in your body, and minimises your risk of breast cancer.
It is important to note that no specific diets or supplements have been linked with a reduction in breast cancer risk. The best advice is to follow a balanced diet with fruit and vegetables.
There is an association between alcohol consumption and the risk of developing breast cancer, amongst many other cancers. Reducing alcohol consumption by limiting alcohol to one standard drink per day, can reduce your breast cancer risk.
Medications to reduce breast cancer risk
The chance of developing breast cancer can be reduced by taking a Selective Estrogen-Receptor Modulator ( SERM) or an Aromatase inhibitor ( AI). Both medications are given orally once per day for for 5 years.
There are 2 SERMs, tamoxifen and raloxifene, and 2 aromatase inhibitors, anastrozole and exemestane, used for breast cancer prevention. Postmenopausal women may choose any 4 of these medications to reduce her breast cancer risk. Premenopausal women are only suitable to use SERMs such as tamoxifen and raloxifene. The risk of breast cancer is reduced by approximately 40% with 5-year use of these medications.
How do SERMs work?
Raloxifene and tamoxifen interfere with the effects of the female hormone, oestrogen, on the breasts. Tamoxifen is also used to treat breast cancer. Raloxifene has been used previously in the treatment of osteoporosis. Both medications also prevent some breast cancer.
Anastrozole and exemestane are aromatase inhibitors and they work by reducing the amount of oestrogen produced by postmenopausal women, resulting in lower exposure of breast tissue to oestrogen.
Both medications have been used to treat breast cancer for many years and have recently been shown to prevent some breast cancers.
It is important that the patient’s individual personal risk is estimated before considering taking risk-reduction medication. Apart from tamoxifen and raloxifene, none of the other medications have been compared directly against each, so comparing their effectiveness is difficult. However, AIs are more effective than SERMs in treating breast cancer and in preventing secondary breast cancer; so it is possible that AIs may be more effective in preventing a first breast cancer also.
A trial that compared tamoxifen and raloxifene directly to each other suggested that tamoxifen was more effective than raloxifene. It prevented 4/10 breast cancers compared to 3/10 with raloxifene.
A trial that compared anastrozole with a placebo (an inactive sugar pill) suggested that anastrozole prevented 5/10 breast cancers. A separate trial that compared exemestane with a placebo (inactive sugar pill) suggested that exemestane prevented 6/10 breast cancers.
The differences in these trials may not necessarily be due to the effectiveness of the medications. The results of the trials may be due to the differences in the trials rather than to differences between effectiveness of the medications. There is longer follow up data available for anastrozole compared to exemestane.
Tamoxifen is known to have a preventative effect of at least 10 years, the 5 years while the tablet is being taken and for at least 5 years after that. The long-term information is not yet available for the use of aromatase inhibitors.
In the trials, very few patients that had a breast cancer predisposition gene such as the mutations in the BRCA1 and 2 gene participated and therefore there is no specific evidence that indicates that this medication is effective for BRCA carriers. However, there have been other studies that have suggested that tamoxifen may reduce the breast cancer risk by a similar amount for women who are carrying mutations in the BRCA gene, but it has not specifically been tested in clinical trials.
Similarly, there have been no studies that have looked at whether raloxifene or AIs are effective in mutation carriers.
There are side effects associated with the medication and it is impossible to predict which women will have these side effects. Most women will tolerate them quite well.
About 1/10 women in the trials stopped the medication due to side effects. The most common side effects are flushes and hot sweats, particularly at night. Flushes may lessen over the first few months of treatment. However, some women indicate that they last for as long as the treatment is taken.
SERMs may increase the rate of vaginal discharge and sometimes itch while aromatase inhibitors can cause vaginal dryness. Aromatase inhibitors can cause aches in the joints. Aching joints are a common reason why women cease aromatase inhibitors and the intensity of the aches can vary from person to person. About 1 in 100 people taking aromatase inhibitors will have carpal tunnel syndrome, which will result in pain and pins and needles in the hand. About 2 in 100 people will develop some diarrhoea or nausea with aromatase inhibitors.
Postmenopausal women taking SERMs may have an increased risk of developing cataracts and aromatase inhibitors may increase risk of dry eyes. Leg cramps, nausea, and rash can be associated with the use of SERMs. Less common side effects include blood clots or deep vein thrombosis.
Aromatase inhibitors do not increase the risk of deep vein thrombosis; however, SERMs slightly increase the risk of blood clots. The risk is 4 per 1000 women for tamoxifen compared to 3 per 1000 women for raloxifene over 5 years. The risk is greater in women who are already at high risk of clots such as those who are smokers or those with a past history of blood clots. Although the risk of blood clots is relatively low, if a clot occurs, a serious side effect can be very rarely a pulmonary embolus which can lead to death. The risk returns to normal levels once the medication is ceased. Having a past history of a deep vein thrombosis or pulmonary embolus or coagulation disorder will be a contraindication to taking SERMs.
There is an increased risk of endometrial cancer with the use of tamoxifen in postmenopausal women. The risk is approximately 4 per 1000 postmenopausal women on 5 years use of tamoxifen. This risk is not seen with the use of aromatase inhibitors and raloxifene.
Aromatase inhibitors can increase the risk of osteoporosis and fractures and therefore it is important to closely monitor bone mineral density while taking the medications. SERMs do not cause osteoporosis but in fact can help to prevent it.
SERMs are are not recommended in patients who have a history of a deep vein thrombosis, pulmonary embolism, or stroke or require anticoagulation or blood thinning medication. They are not recommended in patients that smoke. Patients who take hormone replacement therapy should not be started on tamoxifen.
All postmenopausal patients who have any abnormal gynaecological symptoms such as unusual vaginal bleeding or spotting or pelvic pain or pressure should see their doctor immediately.
Women who are undergoing surgery and taking a SERM should cease the medication 3 weeks before surgery in order to reduce the risk of blood clots. SERMs can be restarted 1 month postoperatively, provided the patient is mobilising. Some medications such as CYP2D6 inhibitor including St. John's wort and other antidepressant medications and over the counter medications may reduce the effectiveness of tamoxifen.
Aromatase inhibitors will only work in postmenopausal women. It is important that women’s postmenopausal state is accurately defined and it is suggested that women who have osteoporosis do not take Aromatase inhibitors. Women are also advised to take calcium and vitamin D supplementation while on aromatase inhibitors.