Commonly used pills for brittle bone treatment could cut breast cancer risk by nearly 40%, US researchers have claimed.
They compared almost 3,000 women diagnosed with breast cancer with a similar number free of the disease, asking both whether they had taken the bisphosphonates pills for the bone thinning disease osteoporosis.
The scientists found a strong link between bisphosphonate use and reduced risk of breast cancer, with the longer a women took the drugs, the more she appeared to be protected. Osteoporosis is most common in older women after the menopause as their levels of oestrogen drop.
Those who used the medication for the longest period - two years - were 40% less likely to develop breast cancer than untreated women, researchers found. Each group's age range was 20 to 69.
Study leader, Dr Polly Newcomb, from the Fred Hutchinson Cancer Research Centre in Seattle, Washington, said: "These medications inhibit the growth of many cell types, and this large study suggests that the development of breast tumours may also be affected."
The findings were reported in the British Journal of Cancer, published by Cancer Research UK.