New figures from Cancer Research UK show that the odds of a British woman developing breast cancer have risen by a fifth over the last twenty years, with around 50,000 new cases likely to be diagnosed this year. But while women today are more likely to develop the disease, their odds of surviving it have improved dramatically too – death rates have nearly halved over the same period.

It’s unclear what is behind the increase in new cases but factors including rising levels of obesity and the trend to having fewer children, later in life (early pregnancy is protective). The fall in the death rate, however, is much easier to explain and due to a combination of the impact of screening, the introduction of specialist breast cancer care services as well as better treatments. And new developments for prevention currently being mooted could soon reduce the toll further.

Despite being able to identify women most at risk of developing breast cancer we have not been able to offer them much up until now, other than close monitoring in the hope that we catch any tumours early, or, in extreme cases, surgical removal of their breasts (mastectomy). But new research currently being considered by advisory groups both here and in America, could see high-risk women being offered daily medication to protect them.

So who is likely to be offered the drugs? How do they work? And, what are the downsides? UK plans are currently under review by the National Institute for Health and Care Excellence (NICE) and due to be announced next month, but the US authorities have already suggested a tentative threshold for offering preventative treatment of a 3% or more risk of developing the condition over a 5-year period – risk is worked out using the National Cancer Institute online tool at .

Access to the calculator is open to the public and results based on the answers to seven questions on subjects ranging from past breast problems, to family history of the disease and whether or not you have had any children, and at what age.

The drugs – tamoxifen, raloxifene and others – work by blocking oestrogen receptors on cancer cells (oestrogen stimulates breast cancer growth and spread in around 8 out of 10 tumours). Think of them as having the opposite effect to fertiliser on a plant, they impede, rather than nurture growth and spread.

Last week a landmark study in The Lancet, which followed 80,000 women over ten years, found that 42 high-risk women would need to take the drugs for five years to prevent one new case of breast cancer – benefit that has to be offset against potential hazards such an increase in blood clots and cancer of the womb (see below).

Whatever NICE’s final decision, medication will only ever be part of a larger preventive strategy that will always include self-help measures. We may not be able to choose our parents and determine our genes, but we can influence other important risk factors. Being overweight, drinking alcohol, a sedentary lifestyle, a poor diet, taking the Pill or HRT, and leaving it late before starting a family all increase the risk slightly, and are potentially within a woman’s control.

I am not suggesting that women have children in their twenties, or become teetotal just to reduce their cancer risk, but those who are worried should be informed that these are influential factors – albeit small ones in the grand scheme. The link with obesity is more important in my view, and one that few women seem aware of despite Cancer Research UK estimating that obesity now accounts for as many as 1 in 10 cases of breast cancer.

And, last but not least, there is vigilance. Make the most of the National Breast Cancer Screening Programme if you are 50 or over, and report any worrying changes in your breasts promptly whatever your age. The earlier the disease is caught, the better the outcome.

 For more information on breast cancer, its treatment and plans to introduce preventative medication visit

 As always the use of preventative medication is about balancing benefit against risk. Current research suggests that for every 1,000 otherwise healthy women deemed to be at high risk of developing breast cancer, and taking tamoxifen for at least 5 years: 

• There would be 21 fewer breast cancers diagnosed over a decade

• But there would be 6 additional blood clots (DVTs)

• And up to 4 additional cases of cancer of the womb