Healthy women at high risk of breast cancer should be given drugs to help prevent them growing tumours, according to a group of international experts.
The controversial move would mirror the practice of prescribing cholesterol-reducing statins to patients in danger of developing heart disease.
Potential preventative drugs for breast cancer include tamoxifen and raloxifene, which target the female hormone oestrogen.
Both are approved in the US for breast cancer prevention but not in the UK.
Tamoxifen has side effects that may include an increased risk of womb cancer and blood clots.
The 12 experts, led by Professor Jack Cuzick, from Queen Mary, University of London, called for the change in a "consensus statement" published in the journal The Lancet Oncology.
They wrote: "To keep the devastating impact of breast cancer to a minimum, especially in the developed countries where prevalence is presently the highest, preventive therapy needs to be integrated into wider strategies of risk reduction, including avoidance of obesity and increase in physical activity."
Four large tamoxifen trials had shown that preventative treatment with the drug reduced the incidence of hormone-sensitive breast cancer by 43%, the authors pointed out.
Crucially, a reduced risk of new tumours had been observed for several years after active treatment ended.
Meg McArthur, from the charity Breakthrough Breast Cancer, said: "It is vital that we find effective ways to prevent breast cancer, especially in women with a high risk. However, as preventative therapy may have negative side effects it would not be appropriate for everyone.
"We welcome studies investigating the best treatments to be used for breast cancer prevention. It's also crucial to identify those at high risk who would benefit the most from this form of therapy."