3D osteocyte lacunar morphometry of human bone biopsies with high resolution microCT: From monoclonal gammopathy to newly diagnosed multiple myeloma

Osteocytes are mechanosensitive, bone-embedded cells which are connected via dendrites in a lacuno-canalicular network and regulate bone resorption and formation balance. Alterations in osteocyte lacunar volume, shape and density have been identified in conditions of aging, osteoporosis and osteolytic bone metastasis, indicating patterns of impaired bone remodeling, osteolysis and disease progression. Osteolytic bone disease is a hallmark of the hematologic malignancy multiple myeloma (MM), in which monoclonal plasma cells in the bone marrow disrupt the bone homeostasis and induce excessive resorption at local and distant sites. Qualitative and quantitative changes in the 3D osteocyte lacunar morphometry have not yet been evaluated in MM, nor in the precursor conditions monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). In this study, we characterized the osteocyte lacunar morphology in trabecular bone of the iliac crest at the ultrastructural level using high resolution microCT in human bone biopsy samples of three MGUS, two SMM and six newly diagnosed MM. In MGUS, SMM and MM we found a trend for lower lacunar density and a shift towards larger lacunae with disease progression (higher 50 % cutoff of the lacunar volume cumulative distribution) in the small osteocyte lacunae 20-900 μm3 range compared to control samples. In the larger lacunae 900-3000 μm3 range, we detected significantly higher lacunar density and microporosity in the MM group compared to the MGUS/SMM group. Regarding the shape distribution, the MGUS/SMM group showed a trend for flatter, more elongated and anisotropic osteocyte lacunae compared to the control group. Altogether, our findings suggest that osteocytes in human MM bone disease undergo changes in their lacunae density, volume and shape, which could be an indicator for osteolysis and disease progression. Future studies are needed to understand whether alterations of the lacunae architecture affect the mechanoresponsiveness of osteocytes, and ultimately bone adaptation and fracture resistance in MM and its precursors conditions.

Multiple Myeloma Spinal Lesion Care: Management of a Primary Bone Malignancy Rather Than a Spinal Metastasis

OBJECTIVE

Multiple myeloma (MM) is too often wrongly categorized as a spinal metastasis (SpM), although it is distinguishable from SpM in many aspects, such as its earlier natural history at the time of diagnosis, its increased overall survival (OS), and its response to therapeutic modalities. The characterization of these 2 different spine lesions remains a main challenge.

METHODS

This study compares 2 consecutive prospective oncologic populations of patients with spine lesions: 361 patients treated for MM spine lesions and 660 patients treated for SpM between January 2014 and 2017.

RESULTS

The mean time between the tumor/MM diagnosis and spine lesions was respectively 0.3 (standard deviation [SD] 4.1) and 35.1 months (SD 21.2) for the MM and SpM groups. The median OS for the MM group was 59.6 months (SD 6.0) versus 13.5 months (SD 1.3) for the SpM group (P < 0.0001). Regardless of Eastern Cooperative Oncology Group (ECOG) performance status, patients with MM always have a significantly better median OS than do patients with SpM: ECOG 0, 75.3 versus 38.7 months; ECOG 1, 74.3 versus 24.7 months; ECOG 2, 34.6 versus 8.1 months; ECOG 3, 13.5 versus 3.2 months and ECOG 4, 7.3 versus 1.3 months (P < 0.0001). The patients with MM had more diffuse spinal involvement (mean, 7.8 lesions; SD 4.7) than did patients with SpM (mean, 3.9; SD 3.5) (P < 0.0001).

CONCLUSIONS

MM must be considered as a primary bone tumor, not as SpM. The strategic position of the spine in the natural course of cancer (i.e., nurturing cradle of birth for MM vs. systemic metastases spreading for SpM) explains the differences in OS and outcome.

Evaluation of mandibular bone changes in multiple myeloma patients on dental panoramic radiographs

OBJECTIVE

The aim of this study is to assess the mandibular bone structures of multiple myeloma (MM) patients on panoramic radiographs using fractal analysis (FA) and radio-morphometric indices.

METHODS

The study group consisted of 67 MM patients, and the control group consisted of 67 individuals without any systemic disease. The mandibular cortical index (MCI) classification, antegonial index (AGI), gonial index (GI), mandibular cortical width (MCW), panoramic mandibular index (PMI) and fractal dimensions (FD) were evaluated on panoramic radiographs. FD measurements were made by identifying 4 related areas. Shapiro-Wilk test was used to determine the normal distribution of the data. Chi-square and independent t tests were used to compare the findings between the two groups.

RESULTS

The FD values of the study group in ROI1, ROI2, ROI3, ROI4 regions and GI values were found to be statistically significantly lower than the control group (p < 0.001). There was no statistically significant difference between the two groups in terms of AGI, MCW and PMI values (p > 0.05). While C1 was the most common type in the control group, C2 was the most common type in the study group. C2 and C3 were detected more in the study group than in the control group (p < 0.001).

CONCLUSION

Our study showed a consensus with the studies advocating that fractal analysis and radio-morphometric indices are methods that can be used to determine mandibular bone density. The low bone density of MM patients is a condition that physicians should be aware of for interventional dental procedures.

Structural complexity of the craniofacial trabecular bone in multiple myeloma assessed by fractal analysis

Purpose

This study aimed to evaluate the structural complexity of craniofacial trabecular bone in multiple myeloma by fractal analysis of panoramic and lateral skull radiography, and to compare the fractal dimension values of healthy patients (HPs), pre-treatment patients (PTPs), and patients during bisphosphonate treatment (DTPs).

Materials and Methods

Pairs of digital panoramic and lateral skull radiographs of 84 PTPs and 72 DTPs were selected. After application of exclusion criteria, 43 panoramic and 84 lateral skull radiographs of PTPs, 56 panoramic and 72 lateral skull radiographs of DTPs, and 99 panoramic radiographs of age- and sex-matched HPs were selected. The fractal dimension values from panoramic radiographs were compared among HPs, PTPs, and DTPs and between anatomical locations within patient groups using analysis of variance with the Tukey test. Fractal dimension values from lateral skull radiographs were compared between PTPs and DTPs using the Student t-test. Pearson correlation coefficients were used to assess the relationship between the mandible from panoramic radiographs and the skull from lateral skull radiographs. Intra-examiner agreement was assessed using intraclass correlation coefficients (α=0.05).

Results

The fractal dimension values were not significantly different among HPs, PTPs, and DTPs on panoramic radiographs or between PTPs and DTPs on lateral skull radiographs (P>0.05). The mandibular body presented the highest fractal dimension values (P≤0.05). The fractal dimension values of the mandible and skull in PTPs and DTPs were not correlated.

Conclusion

Fractal analysis was not sensitive for distinguishing craniofacial trabecular bone complexity in multiple myeloma patients using panoramic and lateral skull radiography.

Clinical significance of trabecular bone score for prediction of pathologic fracture risk in patients with multiple myeloma

Objectives

Osteolytic bone lesions are common complications in multiple myeloma (MM), and can have an impact on quality of life due to the risk of fractures. Trabecular bone score (TBS) is a novel texture index derived from dual energy x-ray absorptiometry (DXA) of lumbar spine (LS) images that provides information about bone microarchitecture. The aim of this study was to evaluate whether TBS is useful in predicting bone fractures in MM patients.

Methods

TBS was calculated retrospectively from existing DXA images of the LS, in 20 patients with newly diagnosed MM. We analyzed the development of fractures in these patients.

Results

The median age of the patients was 66 years (range, 49–77 years). Osteolytic bone lesions were observed in 18 patients (90%) at the time of diagnosis. The median duration of follow-up was 40.0 months (95% confidence interval [CI], 33.2–46.2), 6 fracture events (long-bone fractures in 5 events, vertebral fracture in 1) occurred in 5 patients (25%). There were no significant differences between patients who experienced new onset fractures and patients who did not for all TBSs and T-scores, although the fracture group had lower levels than the no fracture group. However, among TBSs of individual LSs, only L2 showed significantly lower scores in patients who developed fractures (1.135 ± 0.085 [95% CI, 1.030–1.241] vs. 1.243 ± 0.169 [95% CI, 1.149–1.336], P = 0.032).

Conclusions

TBS of the LS in MM patients may be helpful in predicting development of fractures; however, further investigation is needed.

Assessment of Bone Fragility in Patients With Multiple Myeloma Using QCT-Based Finite Element Modeling

Multiple myeloma (MM) is a malignant plasma cell disease associated with severe bone destruction. Surgical intervention is often required to prevent vertebral body collapse and resulting neurological complications; however, its necessity is determined by measuring lesion size or number, without considering bone biomechanics. Finite element (FE) modeling, which simulates the physiological loading, may improve the prediction of fragility. To test this, we developed a quantitative computed tomography (QCT)-based FE model of the vertebra and applied it to a dataset of MM patients with and without prevalent fracture. FE models were generated from vertebral QCT scans of the T₁₂ (T₁₁ if T₁₂ was fractured) of 104 MM patients, 45 with fracture and 59 without, using a low-dose scan protocol (1.5 mm slice thickness, 4.0 to 6.5 mSv effective dose). A calibration phantom enabled the conversion of the CT Hounsfield units to FE material properties. Compressive loading of the vertebral body was simulated and the stiffness, yield load, and work to yield determined. To compare the parameters between fracture and nonfracture groups, t tests were used, and standardized odds ratios (sOR, normalized to standard deviation) and 95% confidence intervals were calculated. FE parameters were compared to mineral and structural parameters using linear regression. Patients with fracture showed lower vertebral stiffness (-15.2%; p = 0.010; sOR = 1.73; 95% CI, 1.11 to 2.70), yield force (-21.5%; p = 0.002; sOR = 2.09; 95% CI, 1.27 to 3.43), and work to yield (-27.4%; p = 0.001; sOR = 2.28; 95% CI, 1.33 to 3.92) compared to nonfracture patients. All parameters correlated significantly with vBMD (stiffness: R²  = 0.57, yield force: R²  = 0.59, work to yield: R²  = 0.50, p < 0.001), BV/TV (stiffness: R²  = 0.56, yield force: R²  = 0.58, work to yield: R²  = 0.49, p < 0.001), and Tb.Sp (stiffness: R²  = 0.51, yield force: R²  = 0.53, work to yield: R²  = 0.45, p < 0.001). FE modeling identified MM patients with compromised mechanical integrity of the vertebra. Higher sOR values were obtained for the biomechanical compared to structural or mineral measures, suggesting that FE modeling improves fragility assessment in these patients. © 2016 American Society for Bone and Mineral Research.

Association of osteolytic lesions, bone mineral loss and trabecular sclerosis with prevalent vertebral fractures in patients with multiple myeloma

PURPOSE

In patients with multiple myeloma (MM), computed tomography is widely used for staging and to detect fractures. Detecting patients at severe fracture risk is of utmost importance. However the criteria for impaired stability of vertebral bodies are not yet clearly defined. We investigated the performance of parameters that can be detected by the radiologist for discrimination of patients with and without fractures.

METHODS AND MATERIALS

We analyzed 128 whole body low-dose CT of MM patients. In all scans a QCT calibration phantom was integrated into the positioning mat (Image Analysis Phantom(®)). A QCT-software (Structural Insight) performed the volumetric bone mineral density (vBMD) measurements. Description of fracture risk was provided from the clinical radiological report. Suspected progressive disease (PD) was reported by the referring clinicians. Two radiologists that were blinded to study outcome reported on the following parameters based on predefined criteria: reduced radiodensity in the massa lateralis of the os sacrum (RDS), trabecular thickening and sclerosis of three or more vertebrae (TTS), extraosseous MM manifestations (EOM), visible small osteolytic lesions up to a length of 8mm (SO) and osteolytic lesions larger than 8mm (LO). Prevalent vertebral fractures (PVF) were defined by Genant criteria. Age-adjusted standardized odds ratios (sOR) per standard deviation change were derived from logistic regression analysis and area under the curve (AUC) from receiver operating characteristics (ROC) analyses were calculated. ROC curves were compared using the DeLong method.

RESULTS

45% of the 128 patients showed PVF (29 of 75 men, 24 of 53 women). Patients with PVF were not significantly older than patients without fractures (64.6 ± 9.2 vs. 63.3 ± 12.3 years: mean ± SD, p=0.5). The prevalence of each parameter did not differ significantly by sex. Significant fracture discrimination for age adjusted single models was provided by the parameters vBMD (OR 3.5 [1.4-8.8], AUC=0.64 ± 0.14), SO (sOR 1.6[1.1-2.2], AUC=0.63 ± 0.05), LO (sOR 2.1[1.1-4.2] AUC=0.69 ± 0.05) and RDS (sOR 2.6[1.6-4.7], AUC=0.69 ± 0.05). Multivariate models of these four parameters showed a significantly stronger association with the development of PVF (AUC=0.80 ± 0.04) than single variables. TTS showed a significant association with PVF in men(sOR 1.5 [0.8-3.0], AUC=0.63 ± 0.08), but not in women (sOR 2.3[1.4-3.7], AUC=0.70 ± 0.07). PD was significantly associated with PVF in women (sOR 1.9[1.1-3.6], AUC=0.67 ± 0.08) but not in men (sOR 1.4[0.9-2.3], AUC=0.57 ± .07). EOM were not associated with PVF (sOR 1.0[0.4-2.6], AUC=0.51 ± .05).

CONCLUSION

In multiple myeloma, focal skeletal changes in low dose CT scans show a significant association with prevalent vertebral fractures. The combination of large osteolytic lesions and loss in radiodensity as can be detected with simple CT Hounsfield measurements of the os sacrum or BMD measurements showed the strongest association to fractures and may be of value for prospective studies.

Association of QCT Bone Mineral Density and Bone Structure With Vertebral Fractures in Patients With Multiple Myeloma

Computed tomography (CT) is used for staging osteolytic lesions and detecting fractures in patients with multiple myeloma (MM). In the OsteoLysis of Metastases and Plasmacell-infiltration Computed Tomography 2 study (OLyMP-CT) study we investigated whether patients with and without vertebral fractures show differences in bone mineral density (BMD) or microstructure that could be used to identify patients at risk for fracture. We evaluated whole-body CT scans in a group of 104 MM patients without visible osteolytic lesions using an underlying lightweight calibration phantom (Image Analysis Inc., Columbia, KY, USA). QCT software (StructuralInsight) was used for the assessment of BMD and bone structure of the T11 or T12 vertebral body. Age-adjusted standardized odds ratios (sORs) per SD change were derived from logistic regression analyses, and areas under the receiver operating characteristics (ROC) curve (AUCs) analyses were calculated. Forty-six of the 104 patients had prevalent vertebral fractures (24/60 men, 22/44 women). Patients with fractures were not significantly older than patients without fractures (mean ± SD, 64 ± 9.2 versus 62 ± 12.3 years; p = 0.4). Trabecular BMD in patients with fractures versus without fractures was 169 ± 41 versus 192 ± 51 mg/cc (AUC = 0.62 ± 0.06, sOR = 1.6 [1.1 to 2.5], p = 0.02). Microstructural variables achieved optimal discriminatory power at bone thresholds of 150 mg/cc. Best fracture discrimination for single microstructural variables was observed for trabecular separation (Tb.Sp) (AUC = 0.72 ± 0.05, sOR = 2.4 (1.5 to 3.9), p < 0.0001). In multivariate models AUCs improved to 0.77 ± 0.05 for BMD and Tb.Sp, and 0.79 ± 0.05 for Tb.Sp and trabecular thickness (Tb.Th). Compared to BMD values, these improvements of AUC values were statistically significant (p < 0.0001). In MM patients, QCT-based analyses of bone structure derived from routine CT scans permit discrimination of patients with and without vertebral fractures. Rarefaction of the trabecular network due to plasma cell infiltration and osteoporosis can be measured. Deterioration of microstructural measures appear to be of value for vertebral fracture risk assessment and may indicate early stages of osteolytic processes not yet visible.

Multidetector computed tomography-based microstructural analysis reveals reduced bone mineral content and trabecular bone changes in the lumbar spine after transarterial chemoembolization therapy for hepatocellular carcinoma

PURPOSE

It is well recognized that therapeutic irradiation can result in bone damage. However, long-term bone toxicity associated with computed tomography (CT) performed during interventional angiography has received little attention. The purpose of this study was to determine the prevalence of osteoporosis and trabecular microstructural changes in patients after transarterial chemoembolization (TACE) for hepatocellular carcinoma therapy using an interventional-CT system.

MATERIALS AND METHODS

Spinal microarchitecture was examined by 64-detector CT in 81 patients who underwent TACE, 35 patients with chronic hepatitis, and 79 controls. For each patient, the volumetric CT dose index (CTDIv) during TACE (CTDIv (TACE)), the dose-length product (DLP) during TACE (DLP (TACE)), and CTDIv and DLP of routine dynamic CT scans (CTDIv (CT) and DLP (CT), respectively), were calculated as the sum since 2008. Using a three dimensional (3D) image analysis system, the tissue bone mineral density (tBMD) and trabecular parameters of the 12th thoracic vertebra were calculated. Using tBMD at a reported cutoff value of 68 mg/cm3, the prevalence of osteoporosis was assessed.

RESULTS

The prevalence of osteoporosis was significantly greater in the TACE vs. the control group (39.6% vs. 18.2% for males, P<0.05 and 60.6% vs. 34.8% for females, P<0.01). Multivariate regression analysis demonstrated that sex, age, and CTDIv (CT) significantly affected the risk of osteoporosis. Of these indices, CTDIv (CT) had the highest area under the curve (AUC) (0.735). Correlation analyses of tBMD with cumulative radiation dose revealed weak correlations between tBMD and CTDIv (CT) (r2 = 0.194, P<0.001).

CONCLUSION

The prevalence of osteoporosis was significantly higher in post TACE patients than in control subjects. The cumulative radiation dose related to routine dynamic CT studies was a significant contributor to the prevalence of osteoporosis.

A longitudinal computed tomography study of lenalidomide and bortezomib treatment for multiple myeloma: trabecular microarchitecture and biomechanics assessed using multidetector computed tomography

BACKGROUND

Bone disease is a common feature in patients with multiple myeloma. In this study, we investigated whether lenalidomide, similar to bortezomib, affects the microarchitecture and biomechanics of bones using clinical CT-based FEM.

MATERIALS AND METHODS

Bone lesions were evaluated using whole-body 64-section multidetector CT scan. For microstructural- and CT/FEM analyses, the volume of interest was defined as a 10-mm thickness of the central part of the L3 vertebral body. Microstructural parameters and mechanical properties were calculated using a 3-D image analysis system. The changes from baseline to the second examination within groups were calculated. Relationships between baseline disease characteristics and percent changes of trabecular parameters were assessed using Spearman correlation analysis.

RESULTS

Thirty-two patients were treated with bortezomib and 18 patients were treated with lenalidomide. At the second CT scan, apparent trabecular number, failure load, and stiffness were decreased in the bortezomib group and failure load and stiffness were increased significantly in the lenalidomide group. In the lenalidomide group, response to chemotherapy was positively associated with increases in failure load (ρ = 0.57; P < .05) and stiffness (ρ = 0.50; P < .05).

CONCLUSION

Lenalidomide treatment resulted in significant increases in CT/FEM-derived estimates of bone strength. Response to chemotherapy predicted lenalidomide-induced bone changes and good responders had increased bone strength.