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Exemestane negatively affects bone health in postmenopausal women
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Postmenopausal women randomly assigned exemestane for the prevention of breast cancer saw significant declines in bone mineral density measurements after 3 years vs. women assigned a placebo, according to recent study findings presented at The American Society for Bone and Mineral Research Annual Meeting.
The findings are an extension of previously published data from a nested, noninferiority bone strength substudy of the same cohort, showing that exemestane had a negative effect on bone health after 2 years.
Miranda Boggild, MD, of the University of Toronto, and colleagues analyzed data from 362 postmenopausal women without osteoporosis or a history of fragility fractures (mean age, 61 years) participating in the MAP.3 trial, a randomized, placebo-controlled study. Researchers randomly assigned 171 women 25 mg exemestane daily; 191 were assigned placebo. After unmasking at 2 years, 79 women crossed over from the placebo group to the exemestane group. Researchers measured total volumetric BMD at the distal radius using high-resolution peripheral quantitative computerized tomography (HR-pQCT) at baseline and 3 years. Researchers used the Kruskal-Wallis test to compare percent change over time.
Within the cohort, the baseline mean areal BMD T-score at the lumber spine as measured by DXA was –0.41; mean score for total hip was 0.12.
After 3 years, total volumetric BMD at the distal radius decreased by a mean of 8.53% in the exemestane group (95% CI, –9.35 to –7.72), compared with a mean decrease of 7.59% in the women who crossed over from placebo to exemestane (95% CI, –8.71 to –6.47) and a decrease of 2.33% in the placebo group (95% CI, –3.93 to –2.04). The decline in secondary bone outcomes continued to the third year of treatment and was significantly different compared with the placebo group, according to researchers.
“Three years of exemestane for the prevention of breast cancer continued to have progressive negative effects on bone despite calcium and vitamin D supplementation,” the researchers wrote. “Further studies with long-term follow-up, including fracture risk, are needed to weigh the risks and benefits of using exemestane for the primary prevention of breast cancer.” – by Regina Schaffer
Reference:
Boggild M, et al. Abstract FR0323. Presented at: The American Society for Bone and Mineral Research Annual Meeting; Oct. 9-12, 2015; Seattle.
Disclosure: Boggild reports no relevant financial disclosures.
Perspective
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Halle Moore, MD
Bone density loss is a known side effect of aromatase inhibitors and appears to be a consequence of further lowering postmenopausal estrogen levels. While this is beneficial for reducing breast cancer risk, it may also increase the risk for developing osteoporosis. For women with breast cancer, the anticipated survival benefit to these medications usually outweighs concerns regarding a possible increase in fracture risk. Medication side effects, including bone density loss, may be of greater concern for healthy women who are taking these drugs for cancer risk reduction rather than cancer treatment. Other chemoprevention options for breast cancer risk reduction include tamoxifen and raloxifene, which actually have beneficial effects on bone density, but these have side effects of their own, including an increased risk for blood clots. Individual patient decisions regarding chemoprevention for breast cancer need to take into account breast cancer risk, risk factors for potential medication side effects and willingness to add additional treatments (such as antiresorptive medications for osteoporosis) should adverse effects occur.
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