Risedronate Reduces Anastrozole-Related Bone Loss in Osteopenic/Osteoporotic Postmenopausal Women
In a substudy of the IBIS-II trial reported in The Lancet Oncology, Sestak et al found that risedronate treatment reduced anastrozole-related bone loss over 3 years in postmenopausal women at increased risk for breast cancer.
Study Details
The study involved assessment of bone mineral density changes among a subgroup of women in the IBIS-II trial. Patients were stratified according to T score: stratum I = ≥−1.0; stratum II (osteopenic) = ≥ −2.5 and < −1.0; and stratum III (osteoporotic) = < −2.5 and > −4.0. All patients were randomly assigned to anastrozole 1 mg/d or placebo, those in stratum II were randomly assigned to risedronate 35 mg/week vs placebo, and all patients in stratum III received risedronate.
Bone Mineral Density Changes at 3 Years
Among stratum II patients, the mean change in lumbar spine bone mineral density at 3 years was +1.1% in 77 receiving anastrozole/risedronate vs −2.6% in 73 receiving anastrozole/placebo (P < .0001) and mean change for total hip was −0.7% vs −3.5% (P = .0001).
Among women in strata I and II who were not randomly assigned to risedronate, mean change in lumbar spine bone mineral density was −4.0% in 310 receiving anastrozole vs −1.2% in 342 receiving placebo (P < .0001), and mean change in total hip bone mineral density was −4.0% vs −1.8% (P < .0001).
Among stratum III patients, mean change in lumbar spine bone mineral density was +1.2% in 46 receiving anastrozole/risedronate vs +3.9% in 60 receiving placebo/risedronate (P = .006), and mean change in total hip bone mineral density was +0.3% vs +1.5% (P = .12).
The incidence of adverse events did not differ between treatment groups within each stratum. No serious adverse events (eg, osteonecrosis of the jaw, serious gastrointestinal events) were observed in patients receiving risedronate.
The investigators concluded: “Risedronate counterbalances the effect of anastrozole-induced bone loss in osteopenic and osteoporotic women and might be offered in combination with anastrozole treatment to provide an improved risk–benefit profile.”
Ivana Sestak, PhD, of Queen Mary University of London, is the corresponding author for the Lancet Oncology article.
The study was funded by Cancer Research UK, National Health and Medical Research Council Australia, Sanofi-Aventis, and AstraZeneca. For full disclosures of the study authors, visit www.thelancet.com.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
