TOPLINE

In a retrospective study of postmenopausal women on aromatase inhibitors (AI), having a body fat percentage over 40% was associated with a doubling of spinal fracture risk. BMI would miss many at high risk.

METHODOLOGY

• Higher BMI is considered protective for bone health, but in women taking AI for breast cancer, evidence suggests obesity raises the risk for fracture — possibly due to adverse metabolic effects of greater adiposity. BMI is an imprecise measure of body composition and may miss many women at particular risk for fracture on AI therapy.
• Researchers looked at whether adiposity, measured by DEXA, was independently associated with vertebral fracture progression among 769 consecutive postmenopausal women with stage I-III breast cancer at their center in Brescia.
• All patients (median age, 63 years) received adjuvant therapy with AI and underwent DEXA at baseline and at 18, 24, and 30 months to evaluate body composition parameters. Excess adiposity was defined as a fat mass percentage greater than 40.8%, and vertebral fracture progression was defined as a new incident fracture and/or worsening of a previous fracture.
• The primary analysis assessed the association between excess adiposity and vertebral fracture, adjusted for variables including age, prior fractures, bone mineral density, and BMI. Secondary analyses explored the associations between vertebral fracture and other body composition measures.

TAKEAWAY

• During a median follow-up of 46 months, 69 patients (9%) had a vertebral fracture progression. After adjustment, a body fat percentage greater than 40.8% was associated with a doubling of fracture risk (hazard ratio [HR], 2.00; P < .001).
• Among women with a BMI < 25, excess adiposity was associated with a markedly increased risk for vertebral fracture progression after adjustment for age, prior fractures, and BMD (HR, 6.63; P < .001).
• Greater appendicular lean mass (muscle mass in the arms and legs) was associated with a reduced risk for vertebral fracture progression (HR, 0.38; P < .001), as was higher bone mineral density (HR, 0.79; P = .01).
• Roughly one third of patients with excess adiposity had a BMI < 30, underscoring the limits of BMI and suggesting it would miss a large portion of patients at high risk for fracture, the study authors noted.

IN PRACTICE

“These findings support incorporating body composition assessment into fracture risk evaluation and preventive strategies for patients undergoing Al therapy,” the authors of the study wrote, adding that the link between appendicular muscle mass and lower fracture risk supports exercise as one such preventive measure.

SOURCE

The study, led by Greta Schivardi, MD, of the University of Brescia in Brescia, Italy, was published online in JAMA Network Open.

LIMITATIONS

Limitations include the retrospective design and the high rate of bone-protecting medication use, leading to a lower-than-expected incidence of vertebral fracture. There was no measurement of visceral adiposity, which has been linked to osteoporosis and fragility fractures — although the findings suggest that excess adiposity, regardless of fat distribution, may adversely affect skeletal health during AI-induced estrogen deprivation.

DISCLOSURES

A co-author received grants from the Italian Ministry of University and Research during the conduct of the study. Other co-authors disclosed financial relationships with Merck, Sanofi, and others outside of the submitted work. Full disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.