Fat Body Mass May Be Associated With Vertebral Fracture in Postmenopausal Women With Breast Cancer

Among patients with breast cancer undergoing aromatase inhibitor therapy, fat body mass may be associated with fragility-related fractures, according to a study published in JAMA Network Open (2019 Sep 4. 2(9):e1911080).

“Aromatase inhibitors induce a profound depletion in serum estrogen levels,” explained Rebecca Pedersini, MD, Medical Oncology Unit, Department of Medical and Surgical Specialties, Radiological Sciences and Public Health, University of Brescia, Spedali Civili Hospital, Italy, and colleagues.

“Postmenopausal obese women receiving aromatase inhibitor therapy may be at increased risk of bone fractures owing to the detrimental association of adiposity with bone quality and the loss of the protective effect of estrogens on bone mineral density,” they added.

In order to examine the association between fat body mass and vertebral fracture prevalence in postmenopausal patients with breast cancer undergoing adjuvant aromatase inhibitor therapy, Dr Pedersini and colleagues conducted a single-center, cross-sectional study.

The study enrolled 556 postmenopausal women with early-stage breast cancer between October 15, 2013, and June 30, 2018. Eligible patients had normal renal function, no metabolic diseases, and no previous or current treatment with antiosteoporotic drugs or glucocorticoids. Prior receipt of chemotherapy was permitted, but no tamoxifen.

Patients were stratified according to receipt of prior aromatase inhibitor treatment: aromatase inhibitor-naïve (n=361) or aromatase inhibitor-treated ≥2 years (n=195).

Patients who received aromatase inhibitor therapy were older than aromatase inhibitor-naïve patients (mean age, 66.1 vs 61.3 years, respectively; P<.001), less likely to exercise (65.3% vs 73.7%, respectively; P=.03), and less likely to consume alcoholic beverages (68.4% vs 80.9%, respectively; P=.001).

Among aromatase inhibitor–naive patients, vertebral fracture prevalence was higher among those with a fat body mass below the median value than in those with high fat body mass. This difference was not statistically significant (19.2% vs 13.3%; P=.13).

In the aromatase inhibitor–treated group the proportion of vertebral fractures was 20.0% in patients with low fat body mass vs 33.3% in patients with high fat body mass (P=.04).

An opposite trend between fat body mass and vertebral fracture was noted using multivariable analysis in the propensity score-matched sample odds ratio (OR), 0.38 (95% CI, 0.12-1.19) and OR, 1.94 (95% CI, 0.67-5.64) in the aromatase inhibitor–naive and aromatase inhibitor–treated groups, respectively.

“Fat body mass may be associated with fragility-related fractures in patients with breast cancer who undergo aromatase inhibitor therapy,” Dr Pedersini and colleagues concluded.

“If these data are confirmed, obesity could be included in the algorithm for assessing fracture risk and selecting patients to receive bone resorption inhibitors,” they added.—Janelle Bradley

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