Multisite validation of biomechanical computed tomography for osteoporosis assessment and fracture prediction in patients with high-risk or metastatic prostate cancer.

Abstract

12044 Background: Long-term androgen deprivation therapy (ADT) among men with high-risk localized or metastatic prostate cancer (PCa) results in a 10-20% risk of significant bone fracture at 10 years. While guidelines recommend routine bone mineral density (BMD) screening for men with PCa receiving ADT, most do not undergo it. We studied whether Biomechanical Computed Tomography (BCT), a radiomic technique to opportunistically measure femoral and vertebral bone strength and BMD from CT scans performed for routine staging, can predict incident fractures among men with PCa beginning ADT. Methods: In this retrospective cohort study among 2 academic cancer centers and 2 Veterans Affairs facilities, we identified 711 men with de novo high-risk localized or metastatic PCa diagnosed between 2010-2018. CT scans at PCa diagnosis were analyzed by BCT. Incident fractures were ascertained by trained radiologists and defined as any new fractures occurring after the initial CT scan. We used Cox proportional hazards models to estimate associations of fragile femur bone strength (≤3500N), fragile vertebral bone strength (≤6500N), or osteoporosis (femoral neck areal BMD T-score ≤-2.5 or trabecular volumetric BMD ≤80 mg/cm3), with incident fracture, adjusted for age, BMI, & race/ethnicity. Results: 673 men were eligible (mean age 69.8±9.3, 49.3% white, 35.2% received prior ADT, 42.3% had prior BMD screening). 198 (29.4%) incident fractures were observed. Using BCT, 123 men (18.3%) had fragile femur bone strength or osteoporosis, and 105 men (15.6%) had fragile vertebral bone strength or osteoporosis by volumetric BMD. BCT-derived fragile femur or vertebral bone strength (adjusted HR 1.81, 95% CI 1.27-2.59) and osteoporosis by BMD criteria (aHR 2.20, 95% CI 1.32-3.62) were associated with incident fracture (Table). Conclusions: In men with high-risk PCa, opportunistic BCT analysis of routine staging CT scans improves osteoporosis detection and fracture prediction, identifying men who may have not otherwise qualified for antiresorptive treatment. BCT is a novel approach to risk-stratify men with PCa for early fracture risk mitigation. Association between BMD and bone strength with incident fracture. Femur Bone Strength HR (95% CI) p-value Normal (≥5000N) 1 (reference) Low (3500-5000N) 1.80 (1.25–2.58) 0.002 Fragile (≤3500N) 2.50 (1.59–3.93) <0.001 Vertebral Bone Strength Normal (≥ 8500N) 1 (reference) Low (6500–8500N) 1.09 (0.60–1.99) 0.78 Fragile (≤6500N) 1.71 (0.96–3.25) 0.07 Femoral Neck BMD (T-score) Normal (≥ –1.0) 1 (reference) Low Bone Density/Osteopenia (–1.0 - –2.5) 1.92 (1.38–2.67) <0.001 Osteoporosis (≥ –2.5) 2.20 (1.32–3.62) 0.003 Vertebral Trabecular BMD Normal (≥120 mg/cm 3 ) 1 (reference) Low Bone Density/Osteopenia (80-120 mg/cm 3 ) 0.99 (0.53–1.84) 0.98 Osteoporosis (≤80 mg/cm 3 ) 1.95 (1.04–3.67) 0.04