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Early results show promise in reducing side effects from anastrozole

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by Cancer Research UK | News

13 December 2007

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A common osteoporosis drug can shield women against the loss of bone mineral density – a side effect of the drug anastrozole which is taken to prevent breast cancer in the IBIS-2 study – according to new data presented at the San Antonio Breast Cancer Symposium.

The data being presented are from the IBIS-2 Bone Sub Study. IBIS-2 is a breast cancer prevention trial looking to see if the drug anastrozole can prevent breast cancer in women at high risk of the disease. The bone sub study has been designed to examine the effects of anastrozole on bone mineral density and whether the extra risk of developing osteoporosis or fractures among women taking part in IBIS-2 can be reduced or even eliminated.

Early results showed that after one year on the trial those women taking a type of osteoporosis drug called bisphosphonate had increased bone mineral density. This increase is despite the women starting the trial with low bone mineral density and being at higher risk of osteoporosis.

Anastrozole is currently only used as a treatment for breast cancer and the only women in the UK using the drug for prevention are those taking part in the IBIS-2 trial. Anastrozole works by blocking the production of oestrogen. By reducing the levels of oestrogen in the body the researchers are hoping to stop those breast cancers that rely on oestrogen from growing. It is also this reduced level of oestrogen that can reduce bone mineral density.

Dr Shalini Singh, who leads the bone sub study and presented the data, said: “Research into the effect that anastrozole has on women’s bones and the extent to which a bisphosphonate can help counter this continues. These preliminary, one year data are encouraging though and we look forward to the three year results to see if this effect is maintained.”

Professor Jack Cuzick, IBIS-2 co-chairman, who is based at Cancer Research UK’s centre for Epidemiology, Mathematics and Statistics, said: “Although these are still very early results, they are reassuring for women participating in the IBIS-2 trial and also for those who may be taking anastrozole as part of their treatment for breast cancer. We still need more eligible women to come forward and take part in this study, which aims to provide them and future generations with valuable information on how to help prevent and control breast cancer.”

For more information on the trial, please visit the IBIS website, CancerHelp UK or call the Cancer Research UK cancer information nurses on 0808 800 4040.


For media enquiries please contact the Cancer Research UK press office on 020 7061 8300 or, out of hours, the duty press officer on 07050 264059.