Vertebral fractures and trabecular microstructure in men with prostate cancer on androgen deprivation therapy

Abstract

Androgen deprivation therapy (ADT), a treatment for prostate cancer, is associated with bone loss and fractures. Dual-energy X-ray absorptiometry (DXA)-measured bone mineral density does not assess vertebral fractures (VF). High-resolution micro-magnetic resonance imaging (HR-MRI) assesses bone microarchitecture and provides structural information. To determine if VF identification increased the diagnosis of osteoporosis beyond DXA and if HR-MRI demonstrated skeletal deterioration in men with VF, we cross-sectionally studied 137 men aged ≥ 60 years with nonmetastatic prostate cancer on ADT for ≥ 6 months. Vertebral fracture assessment (VFA) by DXA was confirmed with X-rays. HR-MRI of the wrist included bone volume to total volume (BV/TV), surface density (trabecular plates), surface/curve ratio (plates/rods), and erosion index (higher depicts deterioration). VF were found in 37% of men; the majority were unknown. Seven percent of participants were classified as osteoporotic by hip or spine DXA. Thirty-seven percent of men without osteoporosis by DXA had VF identified, suggesting that 90% of patients with clinical osteoporosis would have been misclassified by DXA alone. By ANOVA comparison across VF grades, the BV/TV, surface density, and spine, hip, and wrist DXA were lower, and erosion index was higher in men with moderate-severe VF compared with lesser grades (all p < 0.05). By unadjusted ROC analysis, the addition of HR-MRI to DXA at the spine, hip, and femoral neck added substantially (AUC increased 0.831 to 0.902, p < 0.05) to prediction of moderate-severe vertebral fracture. HR-MRI indices were associated with spine, hip, and wrist DXA measures (p < 0.01). Longer duration of ADT was associated with lower BV/TV, surface density, and surface/curve ratio (p < 0.05). ADT for men with prostate cancer is associated with silent VF. DXA alone leads to misclassifications of osteoporosis, which can be avoided by VF assessment. HR-MRI provides a novel technique to assess deterioration of structural integrity in men with VF and adds micro-structural information.