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Wolfson Institute of Preventive Medicine - Barts and The London

Bone density loss from Anastrozole partially reverses after treatment stops

A study published in the British Journal of Cancer shows that bone loss known to be associated with the use of the breast cancer prevention drug Anastrozole partially reverses, particularly at the lumbar spine, after stopping treatment. Anastrozole is a hormone treatment recommended by NICE to prevent breast cancer in high-risk postmenopausal women. A sub-study of 1410 women from the International Breast cancer Intervention Study (IBIS-II) investigated bone density in women who had completed anastrozole treatment. At the seven-year mark, two years after women stopped treatment, the study found that those with weakened bones experienced an increase in bone density at the lumbar spine. The increase did not occur at the total hip. The results suggest that decreased bone mineral density due to anastrozole treatment improves after anastrozole treatment is stopped.

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Lead author Ivana Sestak said: “Overall, anastrozole-related bone loss seems to be manageable. Any risk to bone health should be weighed against overall efficacy and tolerability for the preventive treatment of at high-risk women. This knowledge will help physicians and women who are eligible to take this drug to have a full picture of its effects, so that risks and benefits can be discussed in the decision-making process.”

Ivana Sestak, Glen Blake, Raj Patel, Jack Cuzick, Anthony Howell, Robert Coleman, Richard Eastell.  Off-treatment bone mineral density changes in postmenopausal women receiving anastrozole for 5 years: 7-year results from the IBIS-II prevention trial. Br J Cancer 2021