Breast Cancer Prevention & Risk

CAN BREAST CANCER BE PREVENTED?

Introduction

There is not one single cause for breast cancer; rather it appears to be the combination of several different factors working together. Breast cancer is caused by the interplay of your genes, your environment and chance. The environmental factors are a combination of triggers linked to Western diet, lifestyle and culture. This means that, at the present time, there is no one single thing that you can do to prevent getting the disease.

HOWEVER

An understanding of the factors that cause breast cancer may allow you to lower your risk and help prevent the disease step by step.

Understanding Risk

There are different ways of looking at breast cancer risk.

Lifetime risk

Lifetime risk is the chance that you will get breast cancer at any time during your entire life. In the UK and northern Europe the risk is sometimes referred to as a 1 in 9 lifetime risk. However this figure includes women diagnosed with DCIS (pre-invasive cancer that may never progress to invasive cancer) and women over 85 years of age (when breast cancer may not alter life expectancy), and so at Genesis we prefer to use the figure 1 in 10 lifetime risk as a more realistic reflection of UK risk.

Relative risk

In the following section on Risk Factors, risk is often referred to as relative risk. This means that the extra 'relative risk' needs to be calculated relative to the background risk that the individual concerned starts off with.

For example, the extra 20% risk of breast cancer caused by the contraceptive pill sounds alarming at first glance. However, if you are 25 years of age your background risk of developing breast cancer at all is extremely small; perhaps around a 0.1% chance over the next 10 years. The extra risk from the pill only increases the risk by 20% of 0.1% which is 0.02% extra (or put another way, a 1 chance in 5,000). This is such a tiny extra risk that it may not influence your life decisions.

Absolute risk

Another way of expressing risk is your absolute risk over a period of time. For example, if you are 30 years of age your absolute risk of breast cancer is typically around a 2% chance between the ages of 30 and 50. Or, if you are 50 years of age your risk will be 5% between the ages of 50 and 70.

The single most important factor that increases your absolute risk is a strong family history. Thus, if a close family member had breast cancer at a young age, your own risk might double from 2% to 4% between 30 and 50 years of age and this would entitle you to early mammography screening from 40. Thus, something else that increased your relative risk by 20% has a bigger effect if you have a higher background absolute risk. If your absolute risk is higher than average, then it may become even more important to lower the risk factors in your life that influence relative risk. You can get an idea of your individual background risk from the website www.breastcancerprevention.org

Armed with this information we hope that the relative risks described in this section will make more sense!In the future, we hope that dramatic reductions in risk can be achieved - and thus the vision of the Genesis Appeal is to make 1 in 10, none in 10.

In order to do this it is important to explain the factors that increase or lower breast cancer risk (click on the headings below to read more)


Age at 1st Menstrual Period (Menarche)

The younger a woman starts having periods the higher your risk of breast cancer in later life. The average age of menarche has been falling steadily in developed countries over the last century, probably as a result of better nutrition.

The relative risk for breast cancer is reduced approximately by 7% for each year that menarche is delayed after 12 years of age.
Back to Factors >>

Age at Menopause

The younger your age of menopause, the lower your relative risk of breast cancer. This effect is seen regardless of whether you have had a natural menopause or one induced by surgery. If you have an early menopause and use HRT up until the age of 50, your risk of breast cancer is the same as someone who had a natural menopause at 50.
Back to Factors >>

Age at First Birth

The younger you are when you start child bearing, the lower your risk of breast cancer. This may be one of the factors that means breast cancer has been steadily rising in instance in Western countries over the last few decades, because the average age of having your first baby has steadily risen over this time. The extra risk is estimated to be around 3% relative increase in risk for each year of delay. For example, a woman who has her first baby at age 30 would have a 5x3% = 15% additional theoretical risk compared to a woman who had her first baby at 25, all other factors being equal.
Back to Factors >>

Number of Pregnancies

The more full time pregnancies you have had, the more your potential protection from breast cancer. Even in the absence of breastfeeding, there appears to be a relative reduction in risk by about 7% for each child birth compared to someone who has not had children (nulliparous). Overall, there may be a 30% increase in risk comparing nulliparous women with those who have had children.
Back to Factors >>

Breastfeeding

Breastfeeding appears to confer a degree of protection against breast cancer. The amount of benefit appears to be around 4% reduction in relative risk for every year that has been spent breastfeeding. Breastfeeding three children for 2 months each will thus have hardly any effect on your breast cancer risk, but breastfeeding for one year each would reduce your theoretical risk by 12%.
Back to Factors >>

Contraceptive Pill

The contraceptive pill slightly increases your risk of breast cancer. The extra relative risk is about 20% in current users of the pill. However, because the pill tends to be used in young women whose background risk of breast cancer is very small, this amounts to only a very few extra cases of breast cancer. The risk associated with the pill falls once you have stopped taking the pill, and falls back towards normal after 5 years or more.

For women who are concerned about their breast cancer risk, it is sensible to plan to stop using oral contraceptives at around 30 years of age. Below this age, the extra risk is very small indeed. However, your background risk of breast cancer increases as you get older and so the additional risk of using the pill becomes relatively higher.
Back to Factors >>

HRT

HRT use also increases the risk of breast cancer for current users. This additional risk is seen particularly with oestrogen/progesterone combinations. Once HRT has been stopped, the risk reduces back down to the average risk over the following few years.

The risk rises with the more years of HRT use. Nevertheless, HRT use can have many benefits and so this potential risk needs to be balanced against those potential benefits.

For women who have never used HRT, the risk of breast cancer is 45 per 1000 women between the ages of 50 and 70 years. The additional numbers of breast cancers diagnosed between these ages per 1000 women who began to use HRT at age 50 is an extra two cases (after 5 years use) 6 cases (after 10 years use) or 12 cases (15 years use).

As you can see, the level of risk is very small for women who have used HRT for only 5 years. The decision about HRT use therefore requires a careful balance of potential benefits and potential risks. As a general rule, women for whom breast cancer risk is a concern should limit their use of HRT to perhaps no more than about 5 years.
Back to Factors >>

Western Diet

As countries become more developed and westernised, so their risk of breast cancer increases. Some of the most dramatic rises in breast cancer incidence are now being seen in such developing countries. Women who migrate from a low incidence country into a western country also see a dramatic rise in their risk.

One of the principle reasons for this appears to be western diet. The main culprit is not any particular food item or additive but simply the high fat content and high calorie content of a typical western diet and perhaps the availability of fast foods and snacks. This in turn increases average body weight. The extra risk caused by being overweight seems to be confined to post-menopausal breast cancer. The extra relative risk is around 30% for women who have a body mass index (BMI) over 28 compared to women with a BMI of less than 21.

Modifying your diet to lower your weight or maintain a healthy body weight may therefore be one practical way in which you can lower your breast cancer risk.

There have been several studies looking at individual components of diet such as saturated fat, vitamins, antioxidants, milk, soya, fibre content and additives.

No strong link between any of these components and breast cancer has ever emerged. There are good theoretical grounds for believing that a diet rich in fresh fruit and vegetables such as a Mediterranean style diet has health benefits that may include a lower risk of cancer. At a practical level, switching away from processed or convenient foods towards fresh foods may be another practical way to keep healthy.

For more information about diet read The Genesis Breast Cancer Prevention Diet, which features the findings of Genesis Dietitian Dr Michelle Harvie and is available from the Genesis Appeal, call 0161 291 4400.
Back to Factors >>

Physical Activity

Another feature of western lifestyle is that we tend to take less physical activity compared to previous generations. There is now good evidence that physical activity has a protective effect against breast cancer. This may partly be through controlling body weight, but also appears to be due to a positive effect on body hormone levels. Building regular physical activity into your weekly routine therefore seems to be another practical way in which you can lower your individual breast cancer risk.
Back to Factors >>

Environmental Chemicals

Studies looking at environmental chemicals such as pesticides, fertilisers and preservatives have as yet not shown any direct link with breast cancer.

One example is the group of preservatives known as parabens, which are found in a number of skin creams, deodorants and personal care products. Research funded by the Genesis Appeal has not shown any direct link between deodorants and breast cancer. Nevertheless, such chemicals can be found in breast tissue and indeed may accumulate in this tissue. The level of risk associated with these chemicals is unknown.
Back to Factors >>

Breast Implants

Studies of women who have had silicone breast implants show that they have no increased risk of breast cancer. They do however present a small problem for women who are having regular screening mammogram, because they lower the accuracy of that test. Perhaps about 10% of breast tissue is not seen as clearly on a mammogram in someone with breast implants.

On the other hand, this negative effect may be compensated for by the fact that women with implants tend to have a smaller overall natural breast volume, which is displaced forward making breast examination easier. At a practical level, this theoretical problem should not deter someone from undergoing breast reconstruction surgery using an implant if, for example, they have had a mastectomy. It may be a consideration for those women with a strong family history who are contemplating cosmetic breast augmentation, and a reason not to proceed unless you are really sure of the benefit.
Back to Factors >>

Alcohol

Several studies now have shown that breast cancer is linked to alcohol intake. Women who are tee-total have a lower risk of breast cancer compared to those who drink alcohol. The level of risk rises with the level of alcohol intake, and no particular level of alcohol intake is completely risk free. The extra relative risk appears to be around 7% for each alcoholic drink that is consumed on a daily bases. The extra level of risk is small if you are drinking sensibly and within government guidelines.

If you drink one bottle of wine per day, your increased risk of breast cancer may be 30% relatively greater compared to someone who does not drink at all. For women concerned about breast cancer risk, it therefore makes sense to follow a low alcohol lifestyle, not necessarily teetotal, but certainly within government guidelines.
Back to Factors >>

X-rays

The risk of cancer is increased in people who have had an excessive exposure to ionising radiation. This leads to an understandable concern that too many mammograms could in themselves increase the risk of breast cancer. Thankfully, the dosage of x-rays received in a mammogram is low. It has been estimated that an individual would need to undergo 25,000 mammograms to produce a breast cancer.

Studies looking at the UK population as a whole, taking into account all diagnostic x-rays and scans as well as mammograms, suggests that 1:1000 breast cancers may be attributed to such diagnostic x-rays. Although this level of risk if extremely small, it is sensible advice to avoid having unnecessary x-rays and to avoid having regular mammograms until; if possible, you are over 35 years of age.
Back to Factors >>

Hodgkin's Disease

If you are a woman who was treated for Hodgkin's disease before you were 35 years of age, you may have received ionising radiation as part of your treatment. The cure rates following such treatment are extremely good. However, the subsequent lifetime risk of developing breast cancer in increased so that as many as 1:3 of such women may develop breast cancer. You are therefore eligible to have special surveillance within the NHS.
Back to Factors >>

Affluence

The risk of breast cancer is higher in women from more affluent backgrounds compared to those living in deprived areas. This almost certainly is a reflection of differences in nutrition and reproductive factors as listed above.
Back to Factors >>

Breast Density

The density of breast tissue can be calculated by looking at a standard mammogram. Women with denser breasts have a higher risk of breast cancer compared to those with less dense breast tissue. Part of this increased density is related to genetic factors and part to hormonal factors (such as menopausal status or being on HRT).
Back to Factors >>

Previous Breast Lumps

The majority of lumps in the breast are harmless (benign) and carry no associated increased risk of breast cancer. Two examples of such lumps are fibroadenomas and breast cysts, both of which are completely harmless.

Women who have multiple cysts over a period of several years do have a slightly increased risk of breast cancer. If you are in this category, it is sensible advice to continue having regular mammograms and check-ups until the tendency to cyst formation has settled down.

There are also some more unusual types of breast lump that do have an associated increased risk of breast cancer. These are known as 'proliferative' breast disease or 'atypical hyperplasia'.

If you have had such a lump, your risk of breast cancer may be between two to five times greater than the average risk, and so regular mammogram surveillance is recommended.
Back to Factors >>

Personal History of Breast Cancer

If you have had breast cancer once in the past, your risk of developing a second primary breast cancer in the opposite breast is around 0.5% risk per annum, in other words, after 10 years, a 5% risk and after 20 years a 10% risk. This level of risk can be almost halved if you have taken Tamoxifen regularly for a 5 year period. Thus, after a 20 year period your risk would only be 5%. For a woman who has previously had breast cancer, it does therefore make sense to continue having regular mammograms throughout the rest of your lifetime.
Back to Factors >>

Family History

Women with a family history of breast cancer have a higher risk of developing the disease. Thus, if your mother or sister has had breast cancer, your relative risk may be double that compared to a person with no family history. However, 85% of women with an affected first degree relative (mother or sister) will never develop the disease and over 85% of breast cancer patients have no family history at all.

In a small number of women with a particularly strong family history, the risk of breast cancer may be caused by a mutation in a BRCA1 or BRCA2 gene. If you come from a family where breast cancer has affected several family members, then you should ask your GP for a referral to a genetic clinic where gene testing can be provided on the NHS.

Recent research suggests that, even in the 85% of women with no family history at all, there may nevertheless be an underlying genetic predisposition caused by tiny faults or variations in genetic makeup known as 'SNPS'. Women who carry several such SNPS may have a much higher chance of breast cancer than those who carry none, and yet have no family history of the disease to indicate that such a genetic predisposition might be present.

In the future, it may be that testing for SNPS will become a useful means of early detection of the disease.
Back to Factors >>