Anastrozole is a hormone treatment recommended by NICE to prevent breast cancer in high-risk postmenopausal women.

The results, published in the British Journal of Cancer, are from a sub-study of 1,410 women from the International Breast cancer Intervention Study (IBIS-II) which 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.

Lead author Ivana Sestak from the Queen Mary University of London said: "Overall, the 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."