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. A recent American study (Women's Health Initiative) has shown that taking HRT increases the risk of breast cancer and coronary heart disease. Therefore the author believes that the benefit-risk balance for HRT is negative and that the lowest dose should be used for the shortest time if required.
Lifestyle Risk Factors
Obesity
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.)
Diet
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.
Alcohol Consumption
Recent evidence suggests that excessive alcohol intake increases the likelihood of breast cancer. The risk seems to increase with all types of alcoholic drinks.
Smoking
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
The Environment
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.
It is important to realise that the radiation dose used in mammography (X-rays of the breast) is too small to be a significant risk factor.
Previous Benign 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
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 Table 3.
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 develop
