Variable efficacy of bone remodeling biochemical markers in the management of patients with Paget's disease of bone treated with tiludronate

Bone turnover markers in Paget's disease of the bone: A Systematic review and meta-analysis

The aim of this systematic review and meta-analysis is to study the utility of the commonly used bone turnover markers in evaluating disease activity in patients with Paget's disease of bone before and after treatment with bisphosphonates. We found good correlation between the bone turnover marker concentrations and disease activity assessed by bone scintigraphy.

INTRODUCTION

Paget's disease of bone is a common skeletal disorder of the elderly. Bone turnover marker concentrations are used for diagnosis and follow-up. We aimed to compare the available bone turnover markers and determine their utility in assessing disease activity when compared to quantitative bone scintigraphy.

METHODS

We conducted a systematic review and meta-analysis searching MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus. We evaluated total alkaline phosphatase (total ALP), bone-specific alkaline phosphatase (bone ALP), procollagen type 1 amino-terminal propeptide (P1NP), serum, and urine C-terminal telopeptide (uCTx and sCTx, respectively), and urine N-terminal telopeptide (uNTx). The main outcome of interest was the correlation of disease activity with concentrations of bone turnover markers in Paget's disease patients before and after treatment with bisphosphonates. Correlation coefficients were pooled across studies using the random effects model.

RESULTS

We included 17 observational studies and one trial reporting on 953 patients. Prior to treatment, all studied bone turnover markers had moderate to strong correlation with scintigraphic indices (correlation coefficients ranging from 0.58 to 0.80) with no statistically significant difference between the bone turnover markers overall (p = 0.08). P1NP, uNTx, and bone ALP tend to have higher correlation with scintigraphy. After starting treatment with bisphosphonate, there was moderate to strong correlation with disease activity with all markers except bone ALP (correlation coefficients ranging from 0.43 to 0.70).

CONCLUSION

The findings of this meta-analysis suggest the Paget's disease activity is best monitored by following P1NP levels. However, total ALP, bone ALP, and uNTx are good alternatives as markers of disease activity in untreated patients. Total ALP and uNTx can be useful in following patients with Paget's disease after treatment if P1NP is not available. Clinicians, however, should take availability, cost, and the presence of liver disease into consideration when deciding which bone turnover marker is most appropriate when evaluating patients with Paget's disease.

Biochemical markers to survey bone turnover

Molecular markers of bone turnover have gained increasing relevance in the evaluation of patients with metabolic bone diseases. Their clinical applications include the assessment of future osteoporotic fracture risk, complementation of bone density measurements, diagnosis of certain metabolic osteopathies, therapeutic decision making, and monitoring of therapeutic efficacy and patient compliance. One should be aware, however, that the results from large epidemiologic or clinical trials are sometimes difficult to translate into the everyday clinical situation. The individual patient often has more than one disease that might affect either bone turnover or the handling of the parameters mentioned (or both). Analytic and biologic variability of bone markers can be significant and also needs to be considered when using these indices. In the scientific setting, conventional and new markers of bone turnover can help to elucidate formerly unknown mechanisms and pathways. Because the development of ever more specific and sensitive markers of bone metabolism is progressing rapidly, we are likely to witness new insights into the pathophysiology of bone diseases in the near future.

Non-invasive assessment of equine bone: an update

This paper summarizes traditional and current methods of non-invasive assessment of bone in the horse. The description and potential clinical utility of two non-invasive technologies with major development in the last decade are presented, namely, (1) serum biochemical markers for bone turnover and (2) quantitative ultrasound. Serum biochemical markers of bone formation valid in horses are osteocalcin, carboxy-terminal peptide of type I procollagen and bone-specific alkaline phosphatase. The cross-linked carboxy-terminal telopeptide of type 1 collagen c-telopeptides of type I collagen and total deoxypyridinoline are the serum markers for bone degradation. These markers respond more rapidly to skeletal changes than other bone assessment techniques, but ideally each horse needs to be compared with itself. Quantitative ultrasound is radiation free and is a well-tolerated technique for measuring bone properties in horses. This device allows bone speed of sound measurements at various sites using the axial transmission mode along the cortex and gives information about stiffness, architecture, porosity and bone mass.A combination of different non-invasive assessment techniques is recommended for the evaluation of bone biphasic modelling-remodelling activity and the mineral phase with its architecture. The potential clinical and research use of these techniques is considered.

Short- and Long-Term Effects of Ibandronate Treatment on Bone Turnover in Paget Disease of Bone

Background: In Paget disease of bone (PD), serum total alkaline phosphatase (TAP) is a valid marker of disease activity. The aim of the present longitudinal study was to compare TAP with new and potentially more specific markers of bone turnover in bisphosphonate-treated patients with PD.

Methods: Twenty patients with active PD were studied before and after treatment with 2 mg of intravenous ibandronate over a period of 12 months. TAP (by colorimetry), serum bone-specific alkaline phosphatase (BAP; by enzyme immunoassay), serum osteocalcin (OC; by ELISA), serum bone sialoprotein (BSP; by RIA), and urinary total pyridinoline (PYD; by HPLC) and deoxypyridinoline (DPD; by HPLC) were measured as markers of bone turnover.

Results: Before treatment, TAP, BAP, and BSP were increased in all 20 patients, whereas OC was increased in 10, PYD in 13, and DPD in 15 patients. Three months post treatment, nine patients showed normalized TAP values, and a ≥25% re-increase (i.e., relapse) was observed in all patients after 12 months. A normalization of BAP was achieved in six patients only. No significant changes were found for OC. BSP was decreased significantly at 24 h, and DPD at 48 h post treatment. A normalization of BSP was found in 8, of PYD in 18, and of DPD in 16 cases. Both PYD and DPD increased significantly from 9 months post treatment onward.

Conclusions: Most markers of bone turnover show similar long-term changes after treatment of active PD with ibandronate. With regard to cost-effectiveness and assay performance, TAP remains the marker of choice in therapeutic monitoring of PD. However, more specific markers may improve the biochemical assessment of PD in certain situations.

Short-term therapy with oral olpadronate in active Paget's disease of bone

One of the aims of the treatment of Paget's disease with bisphosphonates should be the normalization of the activity of the disease with the shortest possible exposure to the drug. Olpadronate (OPD) is a new bisphosphonate characterized by the dimethylation of the amino group, its potency is near to alendronate, and more soluble in the digestive media than other aminobisphosphonates. We treated 46 patients (28 men and 18 women, mean age 70 years) with active Paget's disease with oral OPD, 200 mg/day for 12 +/- 2 days, except 2 patients who received 400 mg/day. Eight patients had never been treated before, and 38 had previously received antiosteolytic drugs. The period without treatment prior to OPD was (X +/- 1 SD) 14 +/- 12 months. Baseline bone alkaline phosphatase (BALP) (levels fell from (X +/- 1 SD) 54.0 +/- 62.7 IU/ml (range 22-396) to a lowest mean value of 16.2 +/- 6.4 IU/ml (range 8-45) (normal range 5-21 IU/ml). Forty patients normalized BALP values, in most of the cases within the first 3 months after OPD treatment. Two patients showed partial response (> 50% decrease from baseline), three patients presented poor response (< 50% decrease from baseline), and one patient did not respond at all. Two patients complained of gastric discomfort, and one patient had diarrhea, which disappeared after discontinuation of the drug. Follow-up was carried out on 36 patients; 22 patients are still in remission, with an average length of 9.0 +/- 2.6 months. Fourteen patients experienced relapse after 9 +/- 2 months remission. In conclusion, a 12-day treatment with 200 mg/day of OPD proved to be a very effective and well tolerated therapy of Paget's disease and induced biochemical remissions in the vast majority of patients, even in those with very active disease.

Coccygeal fracture and Paget's disease presenting as acute cauda equina syndrome

Paget's disease of bone affects a significant percentage of adult and elderly patients. Although generally asymptomatic, the inflammatory changes and hypervascularity of the affected bone is prone to pathologic fracture and resultant hemorrhage. Epidural hematoma is well-described with vertebral fractures and can present as acute cauda equina syndrome. We describe a case in which an elderly female with Paget's disease sustained a minor coccygeal fracture and developed local hemorrhage and edema, which caused a sacral plexopathy that presented identical to acute cauda equina syndrome. A literature review will follow.