Breast Cancer Prevention
In Australia, one woman in eleven will get breast cancer, a disease that kills more Australian women than any other form of cancer; 25 new cases are diagnosed every day. Genetic factors play a major role in only a minority of these (only 1-5% of all breast cancers are due to an inherited mutation); the greatest risks come from hormonal, lifestyle, dietary and environmental influences, which to a large degree are controllable and/or avoidable.
Hormones
Breast cancer is a hormonally-driven tumour; its development and growth are stimulated by oestrogens (or at least certain kinds of oestrogens).
In the human body, there are three main oestrogens: oestriol (which comprises some 80-90% of the total circulating oestrogens), a weak oestrogen which appears to have some protective effect (or at worst a neutral effect) in relation to breast cancer risk, and can therefore be regarded as a ‘good oestrogen’; oestradiol (which makes up 7-10% of the total), the strongest oestrogen and most powerful stimulator of breast cancer growth, and therefore (unbalanced) a ‘bad oestrogen’; and oestrone (3-10% of the total), also a strong/’bad oestrogen’.
The overall balance between the good and bad types of oestrogens in the body has an important influence on a woman’s overall risk of developing breast cancer. To complicate things a little further, there are also ‘good’ and ‘bad’ metabolites (breakdown products) of oestrogens in the body - 2-hydroxy-oestradiol and 2-hydroxy-oestrone (good metabolites), and 4-hydroxy-oestrone and 16alpha-hydroxy-oestrone (bad metabolites) - which are also important determinants of breast cancer risk.
In addition to the body’s own (endogenous) oestrogens (and their metabolites), there are also a variety of oestrogenic substances made outside the body (i.e. exogenous oestrogens); again there are good and bad - phyto-oestrogens (from plants, such as soy) have a protective effect and are therefore a good type, whereas chemical xeno-oestrogens (from pesticides, plastics, petrochemicals and various pollutants) are a strong or bad type. Progesterone ( but not synthetic progestogens) is protective against breast cancer.
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