Dual photon absorptiometry for bone mineral measurements using a gamma camera.

A gamma camera was equipped with a special collimator and arm assembly for bone mineral measurements with dual photon absorptiometry (DPA). The system was evaluated in vitro and in vivo and compared both with a rectilinear DPA and a dual energy X-ray (DEXA) system. All 3 systems showed a linear response in measurements of 4 vials, containing different amounts of hydroxyapatite. Phantom measurements with the gamma camera system showed a precision of 1.6% to 2.8%. Results obtained in 8 healthy volunteers with rectilinear and gamma camera systems were well correlated (R2 = 0.78). With the photon beam directed from posterior to anterior, the separation of vertebrae was easy with the gamma camera system. We conclude that bone mineral measurements can be made with a gamma camera for assessment of fracture risk and in the decision process whether a patient needs treatment or not. For follow-up, the precision of DPA with a gamma camera is inadequate.

Palliative pamidronate treatment in patients with bone metastases from breast cancer.

PURPOSE: An open, randomized study was performed to assess the effects of supportive pamidronate treatment on morbidity from bone metastases in breast cancer patients. PATIENTS AND METHODS: Eighty-one pamidronate patients and 80 control patients were monitored for a median of 18 and 21 months, respectively, for events of skeletal morbidity and the radiologic course of metastatic bone disease. The oral pamidronate dose was 600 mg/d (high dose [HD]) during the earliest study years, then changed to 300 mg/d (low dose [LD]) because of gastrointestinal toxicity. Twenty-nine of 81 pamidronate (HD/LD) patients first received 600 mg/d and were then changed to 300 mg/d; 52 of 81 pamidronate LD patients received 300 mg/d throughout the study. Tumor treatment was unrestricted. RESULTS: An overall intent-to-treat analysis was performed. In the pamidronate group, the occurrence of hypercalcemia, severe bone pain, and symptomatic impending fractures decreased by 65%, 30%, and 50%, respectively; event-rates of systemic treatment and radiotherapy decreased by 35% (P < or = .02). The event-free period (EFP), radiologic course of disease, and survival did not improve. Subgroup analyses suggested a dose-dependent treatment effect. Compared with their controls, in pamidronate HD/LD patients, events occurred 60% to 90% less frequently (P < or = .03) and the EFP was prolonged (P = .002). In pamidronate LD patients, event-rates decreased by 15% to 45% (P < or = .04). Gastrointestinal toxicity of pamidronate caused a 23% drop-out rate, but other cancer-associated factors seemed to contribute to this toxicity. CONCLUSION: Pamidronate treatment of breast cancer patients efficaciously reduced skeletal morbidity. The effect appeared to be dose-dependent. Further research on dose and mode of treatment is mandatory.

Improved treatment of Paget's disease with dimethylaminohydroxypropylidene bisphosphonate.

A group of 89 patients with Paget's disease of bone were treated with different intravenous or oral doses of the nitrogen-containing bisphosphonate dimethylaminohydroxypropylidene bisphosphonate (dimethyl-APD). Biochemical remission was obtained in 82% of treatments, and in the rest a clear response was found. Oral dimethyl-APD was well tolerated, and a dose of 200 mg/day for 10 days was sufficient to induce remission in the majority of patients. The remission probability was 3 months for 50% of patients, and the recurrence-free period was 27 months. The remission probability as well as the recurrence-free period did not differ among oral and intravenous treatments or among patients who had never been treated with nitrogen-containing bisphosphonates and those who had received pamidronate in the past and were treated for a recurrence of the disease. Dimethyl-APD is a very effective bisphosphonate devoid of side effects, which given for a short period can induce long-lasting remissions in patients with Paget's disease of bone.

The effect of tissue type plasminogen activator (tPA) on osteoclastic resorption in embryonic mouse long bone explants: a possible role for the growth factor domain of tPA.

Osteoblasts produce proteolytic enzymes and their production is regulated by osteotropic agents. It has been suggested that these proteases play a role in bone resorption by removing the superficial collagenous layer from the bone matrix and indirectly inducing migration of osteoclast precursors towards the bone matrix. We examined the effect of the plasminogen activator tPA on osteoclastic resorption using 17-day-old mouse embryonic long bone explants representing different stages of osteoclast development, that is, radii containing already mature osteoclasts and metacarpals containing no mature osteoclasts but only osteoclast precursors/progenitors which are still confined to the periosteum. Tissue type PA stimulated osteoclastic resorption (measured as 45Ca-release) in 17-day-old fetal metacarpals but not in radii of the same animal. Blocking the enzymatic activity of tPA did not inhibit its effect on osteoclastic resorption. Plasmin, the direct product of PA enzymatic activity, did not induce osteoclastic resorption. However, a tPA-mutant missing the growth-factor-like domain of the molecule, failed to stimulate 45Ca-release from the metacarpals. In addition, in both systems tPA and transforming growth factor alpha had similar effects on osteoclastic resorption. The finding that tPA stimulated 45Ca-release only in the metacarpals suggests that tPA has an effect on osteoclast formation rather than on the activity of already mature osteoclasts. Under the experimental conditions used this effect seems to be mediated by the growth factor domain of tPA rather than by the enzymatic activity of the molecule.

The use of bisphosphonates in the treatment of osteoporosis.

The efficacy of bisphosphonates in the treatment of conditions characterized by increased osteoclastic bone resorption has been established. Recent evidence indicates that these compounds are also effective in the treatment of patients with osteoporosis. Two main protocols have been tried. One is based on the intermittent administration of the bisphosphonate, which is expected to decrease bone resorption, and give a drug-free period during which bone formation may proceed at a normal rate, leading to a positive calcium balance. The other argues that the resetting of the equilibrium in a cyclical process is, as a rule, incomplete and continuous low-grade suppression of resorption will result in a continuing positive bone balance. Intermittent administration of the first generation bisphosphonate, etidronate, for up to three years increases trabecular bone density, stabilizes it after two years, and appears to reduce the rate of new vertebral fractures in women with postmenopausal osteoporosis. Longer follow-up studies are needed before this beneficial effect is unequivocally established. Continuous administration of the second-generation bisphosphonate, pamidronate, increases spinal bone density in patients with osteoporosis linearly for up to four years, and is associated with a low rate of new vertebral fractures. These results need to be confirmed in controlled studies involving more patients. There are indications that pamidronate given continuously can prevent glucocorticoid-induced bone loss. There is no information about the effects of bisphosphonates on non-vertebral fractures. There are limited data about the use of bisphosphonates in the prevention of postmenopausal bone loss. Extensive studies on efficacy and safety are needed before this treatment is offered as an alternative to hormone replacement therapy.

Modulation of PTH-stimulated osteoclastic resorption by bisphosphonates in fetal mouse bone explants.

We examined the effects of the bisphosphonates Cl2MDP, APD, and Me2APD on osteoclastic resorption in the absence and presence of PTH using fetal mouse osteoclast-free bone explants cocultured with fetal liver as a source of osteoclast precursors. Results revealed qualitative and quantitative differences among the bisphosphonates tested. With Cl2MDP and APD fractional inhibition of resorption (measured as 45Ca release) in the presence of PTH was proportional to that obtained in its absence. In contrast, Me2APD, which is the most potent inhibitor of the three, was found at low concentrations (less than or equal to 5 x 10(-7) M) to enhance the PTH-stimulated osteoclastic resorption. APD as well, at concentrations that could not inhibit resorption, had a similar effect, but Cl2MDP did not. These studies describe a new phenomenon, that low doses of nitrogen-containing bisphosphonates can act synergistically with PTH and enhance osteoclastic resorption. These findings may have clinical implications in the management of patients with increased osteoclastic resorption due to parathyroid overactivity.

Regulation of the production of plasminogen activators by bone resorption enhancing and inhibiting factors in three types of osteoblast-like cells.

Production of proteolytic enzymes by osteoblasts is considered to be important for the initiation of osteoclastic bone resorption. We examined the production of tissue-type (tPA) and urokinase-type plasminogen activator (uPA) activity by three types of osteoblast-like cells (normal rat osteoblasts, rat and human osteosarcoma cells) using a quantitative spectrophotometric assay and a qualitative gel overlay technique. All 3 types of cells released both types of PA-activity into the medium, but normal rat osteoblasts released uPA probably in an inactive form. Treatment with different concentrations of the bone resorbing factors bovine Parathyroid Hormone [1-84], synthetic human Parathyroid Hormone-Like Protein [1-34]. Prostaglandin E2, Interleukin-1 beta, Tumor Necrosis Factor alpha and 1,25-dihydroxyvitamin D3 increased in general the production of both PA's by all three cell types. However, there were differences in the relative potencies of these factors. In contrast, Transforming Growth Factor beta, which inhibits bone resorption, decreased PA-activity in osteoblast-like cells. In all three types of cells, under control as well as under stimulated conditions, a high molecular weight form of PA was demonstrated by the gel overlay technique, most likely a complex of tPA with the PA-inhibitor PAI-1. The uniform increase in production of PA's by osteoblast-like cells in response to bone resorbing factors and its decrease by TGF beta supports the notion that PA's are involved in bone resorption. The exact mechanism however, remains to be elucidated.

Automated comparison of dual-photon absorptiometric studies of the lumbar spine.

An automated image comparison procedure was developed to optimize the precision of bone mineral density measurements by dual-photon absorptiometry. Changed acquisition conditions cause differences between two images to be compared. Alignment of one image with respect to the other is performed by a transformation that involves a rotation, a horizontal or vertical shift, and a correction for the soft tissue level. The best possible transformation is found in a stepwise search, guided by initial estimations of its parameters. After optimum transformation of one image, the region of interest of the other image is applied to both of them. Duplicate measurements of 9 patients and 15 normal subjects were performed; automated analysis yielded improved precision with respect to manual analysis. The coefficient of variation (CV) was also computed. The CV for automated analysis was 2.00% for patients and 1.04% for normal subjects compared to 3.55 and 1.93%, respectively, for manual analysis. For phantoms, the precision was 2.67% for manual analysis and 0.49% for automated analysis.

The effect of supportive pamidronate treatment on aspects of quality of life of patients with advanced breast cancer.

Selective aspects of quality of life during supportive pamidronate (APD) treatment were assessed in breast cancer patients with osteolytic metastases. 144 patients were randomised to a pamidronate group (n = 76) or a control group (n = 68). A questionnaire measuring mobility impairment, bone pain, fatigue and gastrointestinal toxicity was administered at 3-monthly intervals. The analysis focused on changes in these quality of life domains over time. The median follow-up for both groups was 18 months. Mobility impairment and bone pain were significantly less in the pamidronate group as compared with the control group, due primarily to a rapid improvement shortly after initiation of pamidronate treatment. Thereafter, a gradual increase in these symptoms was noted in both groups. Gastrointestinal complaints and fatigue levels were similar over time in the two groups, suggesting that these symptoms are more dependent on disease-related events and cytotoxic treatment than on pamidronate treatment. The results indicate that reduced skeletal morbidity in breast cancer patients during pamidronate treatments is associated with an improvement in selective aspects of quality of life.

Limited precision of lumbar spine dual-photon absorptiometry by variations in the soft-tissue background.

The estimation error due to variations in soft-tissue baseline in lumbar bone mineral content (BMC) measured by dual-photon absorptiometry (DPA) was calculated with a new method of automatic baseline subtraction. In water phantom measurements, the s.d. of the soft-tissue (ST) baseline matched closely (r = 0.98) to the random error, calculated using 44 keV and 100 keV count rates and the directly determined baseline variations. In 21 volunteers and in 70 patients with osteoporosis, the ST variations were larger than the expected random error, revealing a source of error related to the inhomogeneity of soft tissue. The estimation error in BMC caused by ST variations was 0.7% in healthy subjects (mean BMC 40.5 gHA) and 1.5% in patients (mean BMC = 26.4 gHA). These results indicate that ST-related errors are an important limit to the precision of lumbar DPA measurements.

Modulation of the production of a parathyroid hormone-like protein in human squamous carcinoma cell lines by interaction with fibroblasts.

Normal human keratinocytes as well as human squamous cell carcinomas produce a parathyroid hormone-like protein (PLP). However, PLP production by these cells is not a constant phenomenon. Since nothing is known about factors which regulate the production of PLP, in vitro studies were performed with normal keratinocytes and squamous carcinoma cell lines in order to establish conditions under which PLP production may vary. PLP was measured as cyclic AMP production in parathyroid hormone target cells (osteoblasts) which could be inhibited by a parathyroid hormone antagonist. The presence of PLP was confirmed using a radioimmunoassay specific for PLP. Results from the bioassay correlated very well with the data obtained by radioimmunoassay for PLP. The results confirm that human squamous carcinoma cells and normal keratinocytes produce PLP. PLP production appeared to be very sensitive to modulation of coculture of squamous carcinoma cells with fibroblasts. The effect of fibroblasts was not mediated by an effect on squamous carcinoma cell viability. Murine transformed fibroblasts (3T3 cells) as well as human normal foreskin fibroblasts were equally effective in inducing PLP production in these cells. The fibroblastic factor was apparently present in a soluble form in the coculture system which prevented direct cell-cell contact but allowed communication through the medium. Nevertheless, conditioned medium from 3T3 cells failed to induce PLP production by squamous carcinoma cells. This suggests a more complicated interaction between the two cell types than a one way message from fibroblasts to keratinocytes. Production of PLP by a number of squamous carcinoma cell lines was variable and not evidently correlated with the ability of these carcinoma cells to differentiate. Production of parathyroid hormone-like protein not only is the expression of a disturbed metabolism of a specific cell type but also reflects the cell-cell interaction in tumor tissue.

Crystal agglomeration is a major element in calcium oxalate urinary stone formation.

The effects of urines from 36 healthy subjects and 86 calcium oxalate renal stone formers on calcium oxalate monohydrate crystallization kinetics were studied using a seeded crystal growth method in which the solubility, the growth and the agglomeration of the crystals are measured as three separate and system-independent parameters. The urines of healthy subjects were found to increase the solubility and to strongly inhibit the growth and the agglomeration of calcium oxalate monohydrate crystals. The urines of stone formers had a similar effect on the solubility, but a significantly lower ability to inhibit the crystal growth and the crystal agglomeration. Of these two kinetic processes the inhibition of crystal agglomeration was more clearly affected, with 55% of the stone formers having abnormally low values, while the changes in crystal growth inhibition occurred within the normal range. The defect in crystal agglomeration inhibition was related to stone frequency, and urines from patients with very high stone frequency rates had also the most severely impaired ability to inhibit the agglomeration of the calcium oxalate monohydrate crystals. The inhibitory effect of urines on crystal agglomeration was found to be related to its citrate content (r = 0.68, P less than 0.001). All patients with hypocitraturia, except two, had also abnormally low values for crystal agglomeration inhibition. In a group of 15 hypocitraturic stone formers, alkali treatment for a mean period of 18 months resulted in a parallel increase in urinary citrate excretion and in the ability of urines to inhibit crystal agglomeration (r = 0.77, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Application of an in vitro model and a clinical protocol in the assessment of the potency of a new bisphosphonate.

The development of new bisphosphonates for clinical use requires congruence between the results of basic and clinical investigations. We have previously shown that this can be achieved with the use of an in vitro coculture mouse metacarpal resorption system sensitive to the activation of osteoclast precursors together with a clinical protocol in which the rate of decrease in urinary hydroxyproline excess with bisphosphonate treatment is assessed in patients with Paget's disease. In these studies bisphosphonates of known potencies were used. In the present study we have evaluated these approaches prospectively in the assessment of the antiresorptive potency of the new bisphosphonate (3-dimethylamino-1-hydroxypropylidene)-1,1-bisphosphonate (dimethyl-APD). A total of 42 patients with Paget's disease of bone received dimethyl-APD in doses predicted from the in vitro system. A total of 24 patients received the bisphosphonate intravenously (2, 4, and 8 mg/day) in groups of 8 patients each and 18 orally (100, 200, and 400 mg/day) in groups of 6 patients each for 10 days. Dimethyl-APD therapy was highly effective in inhibiting bone resorption. Urinary hydroxyproline excretion reached 30.9 +/- 5.6, 17.1 +/- 3.1, and 2.1 +/- 5.3% of initial excess after 10 days treatment with intravenous dimethyl-APD, 2, 4, and 8 mg/day, and 37.4 +/- 18, 10.4 +/- 8.5, and 13 +/- 4.1% with oral therapy, 100, 200, and 400 mg/day, respectively. Comparison of the antiresorptive potency of dimethyl-APD with that of APD showed that the former is roughly five times more potent, as predicted in the in vitro study.(ABSTRACT TRUNCATED AT 250 WORDS)

Parathyroid hormone (PTH) and PTH-like protein (PLP) stimulate interleukin-6 production by osteogenic cells: a possible role of interleukin-6 in osteoclastogenesis.

Osteogenic cells mediate PTH-stimulated osteoclastic bone resorption by a yet unidentified mechanism. We show that primairy rat osteoblast-like cells and the clonal osteogenic sarcoma cell line UMR-106 produce interleukin-6 (IL-6) and that bPTH(1-84) and synthetic hPLP(1-34) stimulate this production dose-dependently. With both peptides a close relation between IL-6 and cyclic-AMP production was found, though for PTH concentrations higher than 2.10(-8) M a clear dissociation was observed. Significant IL-6 activity was also detected in media of cultures of 17-day-old fetal mouse radii and metacarpals which was clearly stimulated by PTH. The source of IL-6 in these bone explants seems to be the osteogenic (cartilage) cells. Treatment of bone explants with IL-6 induced osteoclastic resorption which, however, depended on the bone resorption system used. This bone resorbing action of IL-6 is exerted probably through an effect on the formation of osteoclasts (osteoclastogenesis) rather than on the activation of already existing mature osteoclasts. We suggest that IL-6 produced by osteogenic cells may be a mediator in PTH-stimulated osteoclastic bone resorption.

Effect of long-term bisphosphonate treatment on morbidity due to bone metastases in breast cancer patients.

The effect of long-term bisphosphonate (APD) treatment on the morbidity from bone metastases in breast cancer patients was studied in a controlled clinical trial. 131 patients were randomized between treatment with APD (300 mg/day orally) or control. Systemic treatment for breast cancer was left to the discretion of the physician. The distribution of cases according to age, receptor status and previous treatment was similar in both groups. Patients were examined at 3-month intervals, while bone scans and radiography of relevant lesions in the skeleton were performed every 6 months. After a median follow-up of 13 months, the morbidity in the treated group was significantly less than in the controls. This concerned the occurrence of hypercalcemia, bone pain and fractures, and the need for radiotherapy of osteolytic lesions. In this interim analysis, APD treatment more than halved the requirement for specific treatment of bone lesions. The treatment is simple and well tolerated at a relatively low dosage. A higher oral dose was precluded due to gastrointestinal toxicity. Because the effect of APD on skeletal morbidity was not complete, efforts should be made to develop more effective and less toxic bisphosphonates.

Maintained improvement in calcium balance and bone mineral content in patients with osteoporosis treated with the bisphosphonate APD.

The effects of the (3-amino-1-hydroxypropylidene)-1,1-bisphosphonate (APD) in osteoporosis were investigated in a series of open studies. Seven patients received a high dose of 600 mg/day of APD orally and showed an increase in calcium balance of 5.5 mmol/day (P less than 0.01) within a period of 10 days. In a group of 14 patients with osteoporosis, receiving a low dose of 150 mg/day of APD continuously, the mean calcium balance rose from -0.72 +/- 0.59 mmol/day before treatment to 1.33 +/- 0.87 mmol/day (P less than 0.005) after 1 year. In 24 patients treated with APD 150 mg/day for a mean period of 3.7 years (range 1.4-6.2) repeated dual photon absorptiometry measurements of the lumbar spine showed a mean rate of increase in bone mineral content of 3.1 +/- 1.0% per year (P less than 0.005). This yearly gain in bone mineral content appeared continuous for several years of treatment. In a comparable group of 19 patients with osteoporosis who also received conventional care and treatment but no APD, no significant changes in bone mineral content were found. Addition of a low dose of APD to conventional treatment of osteoporosis does not only prevent bone loss but induces a continuous gain in bone mass. These results justify long-term prospective studies with uninterrupted low dose APD treatment in osteoporosis.

Precision of dual photon absorptiometry measurements: comparison of three different methods of selection of the region of interest.

To determine the short-term reproducibility of bone mass calculations with dual photon absorptiometry of the lumbar spine (L2-L4), duplicate measurements in healthy subjects were used. Three different methods for selection of region of interest were compared: a rectangular region with variable height and width, an irregular region to be drawn freely by the operator and the standard calculation software supplied with the bone densitometer. Contributions of changes in size and location of the region of interest on calculated bone mineral mass were also investigated. An increase in height of the region by 2 scan lines caused an increase in bone mineral content (BMC) of 8.4% +/- 1.8%. Enlargement in width by 2 pixels in each scan line caused an increase in BMC of 2.5% +/- 1.3%. The difference between these region of interest changes was significant (P less than 0.0005). The use of a rectangular region, optimized to enclose L2-L4 in each person but of the same size in both measurements, resulted in a reproducibility of 1.4% and 0.7% respectively for 2 observers, with an inter observer variation of 1.2%. The reproducibility of the duplicate measurements was worse for the other methods of region of interest selection. A further series of duplicate DPA measurements in normal subjects, but with a standard meal between the measurements, showed a larger variation in the results. Again the reproducibility of the calculations using the rectangular region was better than with the other methods, with much less inter observer variation.(ABSTRACT TRUNCATED AT 250 WORDS)

The reproducibility of single photon absorptiometry in a clinical setting.

The reproducibility of single photon absorptiometry (SPA) results for detection of changes in bone mineral content (BMC) was evaluated in a clinical setting. During a period of 18 months with 4 different sources, the calibration scans of an aluminium standard had a variation of less than 1% unless the activity of the 125I source was low. The calibration procedure was performed weekly and this was sufficient to correct for drift of the system. The short term reproducibility in patients was assessed with 119 duplicate measurements made in direct succession. The best reproducibility (CV = 1.35%) was found for fat corrected BMC results expressed in g/cm, obtained at the site proximal to the 8 mm space between the radius and ulna. Analysis of all SPA scans made during 1 year (487 scans) showed a failure of the automatic procedure to detect the space of 8 mm between the forearm bones in 19 scans (3.9%). A space adjacent to the ulnar styloid was taken as the site for the first scan in these examinations. This problem may be recognized and corrected relatively easy. A significant correlation was found between BMC of the lower arm and BMC of the lumbar spine assessed with dual photon absorptiometry. However, the error of estimation of proximal BMC (SEE = 20.0%) and distal BMC (SEE = 19.4%) made these measurements of little value to predict BMC at the lumbar spine in individuals. The short term reproducibility in patients combined with the long term stability of the equipment in our clinical setting showed that SPA is a reliable technique to assess changes in bone mass at the lower arm of 4% between 2 measurements with a confidence level of 95%.