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Negative BMD effects of preventative anastrozole are partially reversible

The negative effects of anastrozole on bone mineral density (BMD) are partially reversible, suggest the findings of a new study published in the British Journal of Cancer.

The study, led by Centre for Cancer Prevention at Queen Mary University London, found that two years after stopping treatment with 1 mg/day anastrozole for five years, BMD at the lumbar spine improved, whereas total hip BMD stabilised over the same time period in women who did not receive any bisphosphonates.

The International Breast cancer Intervention Study II (IBIS-II) trial recruited 3864 healthy, postmenopausal women at increased risk of breast cancer and randomised them to receive either 1 mg/day anastrozole or matching placebo. Of the full cohort, 1410 women took part in the IBIS-II bone sub-study and stratified into three strata according to their baseline T-score at the spine or femoral neck. Five- and seven-year BMD data were available for a total of 528 women who did not receive risedronate.

The primary objective of this analysis was to investigate whether dual-energy X-ray absorptiometry BMD at the spine and hip changed two years after treatment cessation (between five and seven years) in those who did not receive risedronate.

In women with normal BMD at baseline, an increase in BMD at the lumbar spine after anastrozole withdrawal was observed (1.25%; 95% CI, 0.73%-1.77%; P=.0004), which was larger than in those on placebo (0.14%; 95% CI, −0.29% to 0.56%).

Hip BMD remained unchanged between years five and seven for those previously on anastrozole but continued to decrease in those who had been randomised to placebo (−1.35%; 95% CI, −1.70% to −0.98%).

These are the first results reporting BMD changes after stopping anastrozole in a breast cancer prevention setting.

The authors say they show that the negative effects of anastrozole on BMD in the preventive setting are partially reversible.


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