The risk of developing breast cancer increases with age; an average European woman aged 25 years has a 1 in 15000 chance of developing breast cancer; for a 40-year old woman the risk is 1 in 200, for a 50-year-old woman the chance is 1 in 50, and at the age of 80 years the chance is 1 in 11.
The number of cases of breast cancer is five times higher in Western countries than in Far Eastern countries such as Japan and China. However, Japanese women who move to the USA increase their risk of developing breast cancer, which shows that the environment also plays an important role.
Risk factors are things that increase your chance of developing breast cancer. The main groups are shown in the table below.
|1. Cancer history||2. Hormonal||3. Lifestyle||4. Other|
|• Family history
• Previous breast cancer
|• Age when periods started
• Age at first pregnancy
• Age at menopause
• Use of ‘the pill’
• Use of HRT
|• Obesity after the menopause
|• Genetic abnormalities
• Breast biopsy showing atypical cells
Cancer History Risk Factors
Family History of Breast Cancer
It is thought that up to 5% of all breast cancers are inherited owing to the presence of abnormal genes. These genes are passed on from mother to daughter, so having a first-degree relative (such as a sister or mother) with breast cancer will increase your chance of developing the disease. This is particularly true if the relative develops breast cancer in both her breasts, or before she reaches the age of 45 tears. A family history of breast cancer in a first-degree male relative is also associated with a significant increase in breast cancer risk. Breast cancer in a distant relative has little effect on your breast cancer risk.
Your chance of developing breast cancer doubles if one first-degree relative developed the disease before the age of 45 years. If two first-degree relatives developed the disease before the age of 45 years, then your chance of developing breast cancer is four times greater than normal.
Scientists have identified several genes responsible for transmitting breast cancer. Six of the most important of these breast cancer genes are called BRCA-1, BRCA-2 PALB2, ATM, CHEK2 and P53. This inherited form of breast cancer usually develops before the age of 50 years. If a woman has not developed breast cancer by the age of 50 years, despite having a first-degree relative with breast cancer, it is unlikely that she carries the abnormal gene(s).
The BRCA-1 gene is also associated with ovarian cancer. So, the presence of other types of cancer, such cancer of the womb or ovary, in addition to breast cancer, also suggests the possibility that there is a cancer-causing gene in the family. Testing for breast cancer genes is relatively simple using blood or a saliva sample after genetic counselling. One can be testing for a panel of 30 cancer causing genes and obtain the result within 2 weeks.
Cancer of the Other Breast
This increases the likelihood of breast cancer in the remaining breast.
Hormonal Risk Factors
Starting Periods Before the Age of 11 Years
Women who have a history of starting their periods (menses) before the age of 11 years have a higher chance of developing breast cancer. This is thought to be due to their longer exposure to the female sex hormone oestrogen, which is an established risk factor for breast cancer.
The risk of developing breast cancer increases by 5% for each year of delay in having the first full-term pregnancy. Women who have their first child before the age of 30 years have a lower risk of developing breast cancer than those whose first pregnancy occurs after the age of 35 years. Recent research indicates that breast-feeding also reduces the risk of developing breast cancer.
There is no scientific evidence that pregnancies which end in a spontaneous or induced miscarriage increase the risk of developing breast cancer.
The average age of a woman upon reaching the menopause in western Europe is 50 years. Women who reach the menopause after the age of 53 years have a higher chance of developing breast cancer. Delayed menopause prolongs a women’s exposure to oestrogen – just as does starting periods before the age of 11 years.
The Oral Contraceptive Pill
The taking of the oral contraceptive pill that contains oestrogen within the previous 10 years slightly increases the chance of developing breast cancer. The greater the oestrogen-content in the pill, the higher the risk of developing breast cancer. Again, this is because oestrogen increases the risk of breast cancer. However, breast cancer that develops in contraceptive pill users seems to be less advanced than in non-users.
Hormone Replacement Therapy (HRT)
Taking HRT after the menopause seems to increase the risk of developing breast cancer, especially if it is continued for more than 10 years.
HRT, however, reduces the risk of brittle-bone disease (osteoporosis), bone fractures and large bowel cancer. It also improves the symptoms of the menopause, such as vaginal dryness, hot flushes and depression. It is currently thought that HRT should be avoided where possible in women with a personal or a significant family history of breast cancer. For those women who require HRT for improvement of quality of life, I recommend the use of oestradiol patches or gel plus oral natural progesterone (utrogestan). If the woman had previous hysterectomy then the progesterone is not required.
Lifestyle Risk Factors
Obesity after the menopause increases the risk of breast cancer in women, whereas obesity before the menopause seems to reduce breast cancer risk. In post-menopausal women the body fat is the main source of oestrogen production; so obese women will have more oestrogen on board, thus increasing their breast cancer risk. (The main source of oestrogen production in pre-menopausal women is the ovaries.)
The research studies looking at the issue of diet and breast cancer show conflicting results. However, it is thought that a high intake of saturated animal fats and red meat (especially if overcooked) increases the risk of developing breast cancer, whereas diets high in fibre and vitamins (A, C and E), such as fresh fruits and vegetables, decrease the risk. It is also thought that fish and green tea reduce the risk of breasr cancer.
Recent evidence demonstrates that alcohol intake increases the likelihood of breast cancer in a dose-dependant fashion. The risk seems to increase with all types of alcoholic drinks.
There is increasing evidence that both active and passive smoking increase the risk of breast cancer especially in women younger than 50 years.
There is no evidence that the personal use of hair-dyes increases breast cancer risk.
Other Risk Factors
Earlier we said that Japanese women who had moved to the USA developed a similar breast cancer risk to that of the American population. This indicates that there are powerful environmental factors influencing the risk of developing breast cancer. Apart from diet and life-style, certain chemicals, such as pesticides, are thought to increase the risk. As yet, there is no established evidence to support this link. Exposure to radiation also increases the risk of many cancers, including breast cancer.
Consumption of processed foods, overcooked red meat and animal fats seems to increase the risk whereas the mediterranean diet (nuts, salads, fruits, fish, olive oil) seems to be protective.
Previous Breast Biopsy
The risk of breast cancer is not significatly increased if you have had a previous breast biopsy (surgical) for a benign condition, such a cyst or a simple fibroadenoma. However, the presence of certain microscopic features in a breast biopsy is associated with a higher risk. For example, the risk is increased by 4-5 times if a condition known as atypical epithelial hyperplasia is found in the breast biopsy.
Mammographic density in 75% or more of the breast is associated with an almost fivefold increased risk of breast cancer, and this risk persists for an extended period of time. In addition, for women with extensively dense breasts, the masking effect of dense breast tissue increases the odds more than 17 times of a cancer being missed and then detected by non-screening methods. In such cases the addition of ultrasound scan and MRI imaging to digital mammography should be considered.
The risk factors are summarised in the table below.
What Does ‘Increased Risk’ Mean to Me?
Understandably, women can become very anxious when they are told that they have an increased risk of developing breast cancer. It should be remembered that the normal risk of breast cancer for a woman aged 30-50 years is 1 in 1000 per year. If your risk were to double it would be 1 in 500 per year; in other words, one woman in every 500 would get breast cancer within 1 year.
|Risk factor||Increase in risk of breast cancer|
|Age||× 10 (in the very elderly)|
|Family history||× 2–9|
|Country||× 5 (in Western countries)|
|Cancer in the other breast||× 5|
|Early menses (before 11 years)||× 3|
|Late pregnancy (1st child after 40 years)||× 3|
|Late menopause (after 53 years)||× 2|
|Obesity after the menopause||× 2|
|Contraceptive pill (4+ years when young)||× 2|
|Social Class I & II||× 2|
|Previous benign breast biopsy||× 1.5|
|HRT (10+ years)||× 1.5|
|High alcohol intake||× 1.1–2.0|