Automated Opportunistic Bone Mineral Density Assessment at Low-Dose CT Lung Cancer Screening: Incident Vertebral Fractures and Mortality.

BACKGROUND: Low-dose CT (LDCT) for lung cancer screening enables opportunistic volumetric bone mineral density (vBMD) assessment, but its prognostic value is unclear. PURPOSE: To evaluate fully automated LDCT-derived vBMD for predicting vertebral fractures and its association with mortality in individuals who heavily smoke. MATERIALS AND METHODS: This secondary analysis included 55-74-year-old individuals who heavily smoked (≥30 pack-years) from the CT arm of the National Lung Screening Trial (NLST), a multicenter randomized controlled trial of LDCT versus radiography (participants recruited August 2002 to April 2004). Automated SpineQ software (Bonescreen) was used to measure thoracic and lumbar vBMD (normal, ≥120 mg/cm3; low bone mass [osteopenia], 80 to <120 mg/cm3; osteoporosis, <80 mg/cm3) and vertebral fractures (Genant scale). The outcomes included 1- and 2-year incident vertebral fractures and 6-year mortality (active follow-up to 2009). Poisson and Cox models were adjusted for demographic variables, available comorbidities, and baseline vertebral fractures. RESULTS: The NLST included 26 722 participants in the CT arm, with 21 856 included in the present analysis (mean age, 61 years ± 5 [SD]; 12 854 male participants). The 2-year vertebral fracture incidence (n = 18 211 participants with 2-year LDCT) was 0.9% for those with normal bone mass, 2.0% for those with low bone mass (adjusted relative risk, 2.07 [95% CI: 1.70, 2.53]), and 5.9% for those with osteoporosis (adjusted relative risk, 3.40 [95% CI: 2.69, 4.30]). Mortality risk (n = 21 447 participants with completed follow-up [median, 6.65 years]) was associated with osteoporotic vBMD in men (adjusted hazard ratio, 1.24 [95% CI: 1.02, 1.50]). CONCLUSION: Fully automated opportunistic assessment of spinal vBMD predicted vertebral fracture risk and was associated with mortality in men after adjustment. Individuals with osteoporotic vBMD who heavily smoked had a 2-year fracture incidence above the 5% treatment threshold according to current osteoporosis guidelines. Clinical trial registration no. NCT00047385