Feasibility of opportunistic bone health assessment using low-dose CT trabecular attenuation and 18F-NaF uptake from PET/CT in prostate cancer.

BACKGROUND

18F-NaF PET/CT is widely used in prostate cancer for detecting skeletal metastases, but the examination also contains structural and metabolic information potentially relevant to bone health assessment.

OBJECTIVE

This study evaluated feasibility of this dual-parameter approach for opportunistic bone health assessment in prostate cancer.

DESIGN

This was a retrospective cross-sectional.

METHODS

A total of 105 men with prostate cancer without bone metastasis underwent 18F-NaF PET/CT. Stand-alone diagnostic CT-L1 was available in 76 patients and was used as an external structural reference for feasibility analysis and gray-zone stratification. Patient-level analyses used mean lumbar SUVavg and mean PET/CT-derived trabecular attenuation across L1-L4. Vertebra-level analyses used all available same-level SUVavg and same-level PET/CT-derived trabecular attenuation measurements. Patient-level metabolic-structural discordance on 18F-NaF PET/CT was assessed.

RESULTS

PET/CT-derived L1 trabecular attenuation agreed strongly with stand-alone diagnostic CT-L1, with a correlation coefficient of 0.929 and an intraclass correlation coefficient of 0.916. In the paired diagnostic CT, cross-validated discrimination for low diagnostic CT-L1 thresholds was already high with low-dose CT alone, and adding SUV did not improve performance. However, among 41 patients in the stand-alone diagnostic CT gray zone of 110-160 HU, 19 (46.3%) were classified as low 18F-NaF uptake. At the patient level, mean SUVavg across L1-L4 correlated positively with mean PET/CT-derived trabecular attenuation across L1-L4 (r = 0.521, p<0.001). In the vertebra-level mixed-effects model, each 10-HU increase in trabecular attenuation was associated with a 0.084-unit increase in SUVavg (95% CI: 0.058 to 0.110; p<0.001). Nine patients showed a higher-TA but low-uptake phenotype, whereas 30 showed low TA with higher uptake.

CONCLUSIONS

In prostate cancer, 18F-NaF PET/CT may feasibly support opportunistic bone health assessment by integrating low-dose CT-derived trabecular attenuation and 18F-NaF uptake within the same examination. The clinical contribution of 18F-NaF uptake appears to lie more in refining gray-zone stratification and identifying metabolically discordant patients. These feasibility findings are hypothesis-generating and require prospective validation against DXA and fracture endpoints before clinical use.