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2428. DXA-Derived BMD is Not a Good Predictor of Bone Metabolism
Authors * Denotes Presenting Author
  1. Helene Chesnais *; Penn Medicine
  2. Daniel Kargilis; Penn Medicine
  3. Sofia Miguez; Penn Medicine
  4. Nikita Bastin; Penn Medicine
  5. Chamith Rajapakse; Penn Medicine
Objective:
Individuals with prostate cancer often have poor bone health secondary to bone metastases and androgen-deprivation therapy. Bone Mineral Density (BMD) derived from Dual-energy X-ray absorptiometry (DXA) is the standard of care for determining fracture risk in these patients. However, BMD fails to accurately predict many osteoporotic fractures, especially in the spine [1]. Another imaging modality, 18-F Sodium Fluoride Positron Emission Tomography with Computed Tomography ([18F]NaF PET/CT) is used to monitor metastatic spread but may opportunistically assess changes in bone metabolism to improve the assessment of fracture risk in prostate cancer patients. The purpose of this study was to investigate how much of bone metabolic activity of lumbar spine measured by [18F]NaF PET/CT-derived bone metabolism markers can be explained by DXA-derived BMD in prostate cancer patients.

Materials and Methods:
This study includes 38 male participants (ages 56-83) with a history of prostate cancer and who have undergone both [18F]NaF PET/CT and DXA scans. A PET/CT image processor was used to measure Standard Uptake Values (SUVmean and SUVmax) of the lumbar spine (L1-L4) in the following volumes of interest (VOI): a 3D sphere at the center of the vertebra (20mm diameter) and 2D region of interest encompassing the vertebra in the midline sagittal plane. Lumbar (L1-L4) BMD values and BMD T-Scores were obtained from patient records. Associations were analyzed between BMD, BMD T-Score, and average SUVmean and SUVmax, followed by Bonferroni correction for multiple comparisons. For the L3 vertebra, a reproducibility analysis was conducted between 4 independent graders using both sampling methods and mean coefficients of variation (CVs) were calculated.

Results:
Average Lumbar SUVmean and SUVmax were not correlated with BMD or BMD T-score in either VOI (3D sphere or 2D rectangle). The mean CVs of the 3D sphere reproducibility study were 4.6% and 3.3%, for SUVmax and SUVmean, respectively, and those for the 2D rectangle study were 6.3% and 4.5%.

Conclusion:
Our study reports that DXA-derived BMD and BMD T-score are not good predictors of bone metabolism. This suggests that [18F]NaF PET/CT may provide further information about bone quality that is not captured by conventional densitometric methods. Additional studies are necessary to determine if measures of bone metabolism as measured by [18F]NaF PET/CT can improve fracture risk assessment.