Osteoporosis drugs may help prevent breast cancer

British Journal of Cancer

A drug commonly used to prevent and treat bones losing density and becoming brittle – known as osteoporosis – may also help reduce the risk of breast cancer by one third or more according to new research published in the British Journal of Cancer today (Wednesday).

Researchers found that the women who used the drug for the longest period – two years or more – reduced their breast cancer risk by almost 40 per cent. The effect was present only in women who were not obese.

Nearly 3,000 women diagnosed with breast cancer were interviewed and had their records compared with around 3,000 women who did not have breast cancer. The researchers recorded how many women had used the osteoporosis drugs – known as bisphosphonates – and for how long.

Dr Polly Newcomb of the Fred Hutchinson Cancer Research Center in Seattle, Washington, USA, led the study, which was funded by the US National Institutes of Health. Dr Newcomb 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.”

Earlier studies have shown a reduction in breast cancer recurrence in women receiving a bisphosphonate as part of their therapy. Research has yet to show exactly how they might reduce breast cancer risk.

Dr Lesley Walker, Cancer Research UK’s cancer information director, said: "This is an interesting result but important questions remain about using this type of drug to help reduce breast cancer risk. It’s important that researchers find out more about how these drugs act on cancer cells and whether the drug is only appropriate for certain women. All drugs have potential side effects and before any drug can be recommended to prevent or treat a disease thorough testing needs to be completed."

Professor Jack Cuzick, Cancer Research UK's epidemiologist who leads a breast cancer prevention trial named IBIS-2, said: “This is an interesting finding which has been previously suggested by breast cancer treatment trials where recurrence rates have been reduced with bisphosphonate use. These findings now need to be confirmed with direct randomised prevention trials in high risk women.

“We have begun this in our breast cancer prevention trial in post menopausal women. This focuses on using a drug that stops oestrogen being produced, with a small bone sub-study using a bisphosphonate. Larger studies will be needed to fully evaluate the role of a bisphosphonate in prevention.”

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References

  • Newcomb, P., Trentham-Dietz, A., & Hampton, J. (2010). Bisphosphonates for osteoporosis treatment are associated with reduced breast cancer risk British Journal of Cancer DOI: 10.1038/sj.bjc.6605555

Notes to Editor

There are more than 45,500 women diagnosed with breast cancer in the UK every year.

There are just under 12,000 women who die from breast cancer each year.

IBIS-2 (International Breast cancer Intervention Study II) is a ten year study involving 10,000 healthy women who are at an increased risk of breast cancer.

IBIS-2 is being funded by Cancer Research UK and sponsored by Queen Mary, University of London. The trial is taking place in 21 countries, including Australia, India, Chile, Germany and Italy.

The IBIS-2 Prevention part of the study aims to recruit 6,000 post-menopausal women who are at increased risk of developing breast cancer. A number of factors for increased risk can make a woman eligible to enter the study and these are set according to the different age groups. Women can take part in the trial if they are aged between 40-70 years and are not on HRT.

IBIS-2 DCIS will recruit 4,000 postmenopausal women who have been diagnosed with and had surgery to remove DCIS (Ductal carcinoma in situ). This part of the trial is designed to determine which of the two drugs, anastrozole or tamoxifen, can best prevent new cancers, both in the breast affected by DCIS and in the opposite breast. Women who have had a mastectomy to remove their DCIS cannot join this arm of the trial but they can be part of the prevention part.

The drug being used to stop oestrogen being produced in the IBIS-2 trial is called Anastrozole (trade name Arimidex). Anastrozole is one of a group of drugs called aromatase inhibitors. In post-menopausal women, an enzyme called aromatase is the main source of oestrogen. Aromatase inhibitors block the action of aromatase, reducing the levels of oestrogen in the body.

About the British Journal of Cancer (BJC)

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