Systemic bone loss measured by routine CT is associated with increased pain, postural decompensation, and survival in...

Multiple myeloma (MM) is frequently associated with bone loss, yet the clinical significance of vertebral body bone loss measured in Hounsfield Unit (HU) decline remains underexplored. This study aimed to investigate longitudinal changes in vertebral HU on routine CT scans, and their associations with disease-related parameters, postural alignment, function and survival.

In this retrospective study, 79 MM patients with three sequential whole-body CT scans were analyzed. HU values at vertebral level L1-L4 were assessed, and a ≥ 35% decline was identified via ROC analysis as a clinically relevant threshold influencing clinical outcomes. Subgroup analyses examined the influence of disease activity, steroid use, osteoprotective therapy, renal function, and nutritional status. Associations with pain, spinopelvic sagittal alignment, and survival were evaluated.

HU values declined markedly over time, from 148.6 ± 11.3 HU at baseline to 120.1 ± 10.3 HU at tCT2 and 86.5 ± 11.8 HU at tCT3 (p < 0.0001). Patients with high disease activity showed greater HU loss than those with low activity (- 49.5 ± 8.7% vs. -38.7 ± 11.0%, p < 0.001). Steroid therapy accelerated HU decline (- 47.1 ± 7.6% vs. -40.4 ± 8.4%, p < 0.001), whereas osteoprotective treatment mitigated it (- 36.8 ± 7.2% vs. -42.3 ± 8.9%, p = 0.02). The ROC-derived threshold for clinically relevant bone loss was ≥ 35%, identifying patients with higher pain (VAS 7 vs. 4, p < 0.001), greater analgesic use (WHO score 2 vs. 1, p < 0.001), and more pronounced postural deterioration (ΔTK + 8.3° vs. -0.7°, p < 0.001; ΔLL - 10.6° vs. -2.4°, p < 0.001). In multivariate analysis, ≥ 35% HU loss was independently predicted by high disease activity (OR 2.62, p = 0.006) and steroid exposure (OR 2.11, p = 0.027), while osteoprotective therapy was protective (OR 0.53, p = 0.031). Exploratory survival analysis showed reduced overall survival in patients with ≥ 35% HU decline (p = 0.04).

CT-based HU measurement enables longitudinal assessment of vertebral bone quality and identifies patients at risk for pain, functional decline, and poorer overall prognosis. Furthermore, HU decline increases with disease progression and might serve as additional marker for disease burden and activity.