Thursday, 10 December 2009

Will we be able to prevent breast cancer?

Writing from the San Antonio Breast Cancer Symposium – the opening address was by a distinguished UK scientist, Professor Valerie Beral giving an epidemiological perspective on the causes and prevention of breast cancer.

Her conclusions were deceptively simple. Women who have many children, have them young and breast feed them for long periods of time have a much lower risk of breast cancer. Late pregnancy (miscarriages and abortions have no effect) and breast feeding produce changes in the body which persist indefinitely. This is interesting because while HRT and the contraceptive pill have been shown to produce a slight increase in the incidence of breast cancer once you stop taking them the increased risk goes away until a few years on there is absolutely no increased risk.

Her conclusions are stark – few women in developed countries are at really low risk of breast cancer unless they develop the birth and breast feeding patterns of women in rural developing countries. Clearly that is not going to happen- you can and should certainly breast feed if you have children but are not going to have any or many children simply to reduce our risk.

Another conclusion is that with the gradual urbanization of developing countries and the impact that has on family size, by 2030 we could see the number of breast cancers diagnosed annually worldwide double from one to two million.

There are factors which we can change: if no woman in the USA was obese, drank alcohol or used the pill or HRT there would be 40,000 fewer cases of breast cancer (140,000 against 180,000).

I think this is scientifically interesting and really does point to avenues for research – prevention is the most difficult and expensive avenue of research. But, as Valerie acknowledged, none of this is very helpful to us now – altering childbearing patterns is not a realistic option so interventions which mimic the effects of childbearing and lactation are needed.

Just remember – lies, damn lies and statistics – this is about statistics and it doesn’t mean that no woman who has children and breast feeds will get breast cancer and not all nuns get breast cancer either – I am not being facetious about nuns – the start of this research was an observation in the 18th century that nuns had a much higher risk of breast cancer than married women. That is the basis of epidemiology – scientific observation of what has happened so that you can change what will happen.

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