Radiological evidence of a dose-related response to long-term treatment of Paget's disease with human calcitonin

Management of Paget's disease of bone

Paget's disease is a progressive focal bone condition which can result in pain, low quality of life, deformity and other complications. Disease progression can be halted with potent bisphosphonates, resulting in improvement in both quality of life and pain, and normalisation of scintigraphy, plain radiographs and bone histology. Zoledronate has transformed the treatment of Paget's disease, producing sustained remissions in almost all patients. Thus, it is now possible to normalise bone cell activity and prevent disease progression at low cost, with one or two intravenous injections of zoledronate, greatly reducing follow-up costs. Patients with Paget's disease who are symptomatic or at risk of complications should have the opportunity to reap these therapeutic benefits. Potent bisphosphonates are highly effective in halting disease progression in Paget's disease, but guidelines disagree about treatment indications. The efficacy, safety and low cost of zoledronate recommend its use in any patient who is symptomatic or judged to be at risk of complications from Paget's disease.

Adult Paget's disease of bone: a review

Adult PD of bone is the second commonest metabolic bone condition after osteoporosis. The condition is characterized by increased bone cell activity, with bone-resorbing osteoclasts often larger and containing more nuclei than normal, and osteoblasts producing increased amounts of disorganized bone. This leads to expanded bone of poor quality possessing both sclerotic and lytic areas. PD of bone has a strong genetic element, with a family history being noted in 10-20% of cases. A number of genetic defects have been found to be associated with the condition. The most common disease-associated variants identified affect the SQSTM1 gene, providing insights into disease aetiology, with the clinical value of knowledge of SQSTM1 mutation status currently under active investigation. The diagnosis may be suggested by an isolated raised total ALP without other identifiable causes. This can be confirmed on plain X-rays and the extent determined by isotope bone scan. The mainstays of treatment are the bisphosphonates, especially i.v. zoledronate, which results in long-term suppression of bone turnover. ALP is the usual means of monitoring the condition, although more specific bone turnover markers can be helpful, especially in coincident liver disease. Patients should be followed up to monitor for biochemical relapse or development of complications, which may require medical or surgical intervention.

223Ra-dichloride response in a patient with Paget disease and bone metastases secondary to castration-resistant prostate cancer

PURPOSE

Paget disease is commonly asymptomatic and discovered when an imaging test is performed for another clinical indication or when elevated serum alkaline phosphatase is found. Bone pain usually appears late in the disease process and is only present in a minority of patients. For diagnosis, X-ray and bone scan are the most recommended imaging methods; radionuclide imaging of the skeleton has become the standard, since it is the most sensitive test for detecting increased bone activity. For treatment, either bisphosphonates or calcitonin are recommended.

METHODS

We present a 74-year-old patient diagnosed with prostate cancer in 2001 who developed bone metastases concomitant with a Paget bone disease.

RESULTS

This patient received treatment with Ra-223, having stable disease in bone scan and no relevant toxicities.

CONCLUSIONS

There is no clinical experience with Ra-223 and Paget disease, since it is characterized classically as a high bone turnover disease and therefore there is no rationale to administer a drug that has a high bone affinity. Nevertheless, Ra-223 is not contraindicated.

Improvement of pagetic bone lesions with risedronate treatment: a radiologic study

Risedronate is a potent pyridinyl bisphosphonate in clinical development for treatment and prevention of osteoporosis, and has been recently approved for treatment of Paget's disease in the United States. An open-label study was conducted to determine the effect of risedronate treatment on pagetic bone lesions in patients with moderate to severe Paget's disease (mean serum alkaline phosphatase levels [ALP] approximately seven times the upper limit of normal). Patients were treated with 30 mg/day oral risedronate for 84 days followed by a 112-day nontreatment period. This 196-day cycle was repeated once in patients whose ALP did not normalize or who experienced relapse, defined as a > or =25% increase in ALP from the lowest value measured. Radiographs of affected anatomical sites in 26 patients were collected at baseline, 6 months, and/or 12 months. Eleven patients received one course and 15 patients received two courses of treatment. Radiographs were examined by a skeletal radiologist who was blinded to their time sequence. Changes in pagetic lesions were categorized as "improved," "deteriorated," or "no change." Between baseline and 6 months, 16 patients improved and 3 deteriorated; at 12 months, 11 patients improved and 2 deteriorated. Most lesions remained unchanged between 6 and 12 months. Improvements were noted in all skeletal sites (tibia, femur, humerus, forearm, pelvis, spine, and skull), but were most pronounced in weight-bearing long bones. In weight-bearing bones, nine lesions had osteolytic fronts. Of these, seven improved and two remained unchanged at 6 months; at 12 months, all but one lesion (which improved) remained unchanged. This radiographic assessment demonstrates that oral risedronate, 30 mg/day in one or two 3-month courses, is highly effective for improving bone lesions in patients with Paget's disease. Risedronate treatment had no deleterious effect on osteolytic lesions in weight-bearing bones; indeed, the majority of lesions with osteolytic fronts were improved after 6 months of risedronate treatment.

Treatment of Paget's disease of bone with alendronate

In summary, the clinical efficacy studies provide clear evidence that treatment with oral alendronate markedly suppresses bone turnover and produces clinical improvement in pagetic patients. Serum alkaline phosphatase was greatly decreased by treatment, and the response to alendronate was superior to that observed for currently available therapies such as etidronate and calcitonin, which usually reduce alkaline phosphatase, on average, by 40%-50%. Alendronate also markedly reduced urinary resorption markers and induced radiologic improvement of pagetic osteolysis. A majority of alendronate-treated patients normalized their serum alkaline phosphatase by month 6. This observation is likely to be relevant to the duration of response to treatment, as previous studies have shown that the degree of suppression of alkaline phosphatase after antiresorptive treatment correlates with the duration of remission. Therefore, patients who responded to treatment with alendronate, especially those who normalized their alkaline phosphatase levels, are likely to maintain the biochemical remission for several years. Indeed, preliminary unpublished data seem to indicate that alendronate is capable of producing long-term biochemical remission in the majority of patients. In addition to its efficacy, the safety and tolerability profile of alendronate 40 mg/day was very favorable and, overall, comparable to that of placebo.

Biochemical and radiologic improvement in Paget's disease of bone treated with alendronate: a randomized, placebo-controlled trial

PURPOSE

The potent bisphosphonates offer great promise in the management of Paget's disease of bone, but are currently available only as parenteral preparations in most countries. There is a need for a well-tolerated, oral therapy. Furthermore, none of the currently available therapies have been rigorously demonstrated to heal the lytic bone lesions characteristic of this condition. Alendronate is a potent new oral aminobisphosphonate that has shown promising effects on Paget's disease in preliminary studies.

METHODS

We report a double-blind, randomized comparison of oral alendronate 40 mg/day and placebo over 6 months in 55 patients with Paget's disease. Efficacy was determined from measurements of biochemical indices of bone turnover (serum alkaline phosphatase and urine N-telopeptide) and blinded radiologic assessment of lytic bone lesions.

RESULTS

N-telopeptide excretion declined by 86% and serum alkaline phosphatase by 73% in patients receiving alendronate, but remained stable in patients receiving placebo (P < 0.001 between groups for both indices). Responses were similar whether or not patients had previously received bisphosphonate treatment. Alendronate treatment normalized alkaline phosphatase in 48% of patients. Forty-eight percent of alendronate-treated patients showed radiologic improvement in osteolysis whereas in the placebo group only 4% improved (P = 0.02 for between-groups comparison). No patient in either group showed worsening of osteolysis. Bone histomorphometry indicated that alendronate tended to normalize turnover indices. There was no evidence of abnormal mineralization in bone biopsies taken from 12 alendronate-treated subjects. The treatment was well tolerated.

CONCLUSION

Oral alendronate appears to be a safe and effective therapy for Paget's disease and results in healing of lytic bone lesions.

Paget's disease of bone

Paget's disease is a relatively common bone disease. This review aims to present reasonable treatment recommendations with enough background to understand them. To accomplish this end, some aspects of basic bone cell biology, biochemistry, and pathology are presented, as are speculations about possible causes of this disease. Treatment of Paget's disease will be considered in three sections. The first two sections will review treatment with calcitonin and diphosphonates, respectively. These sections briefly will consider the mechanism of action of the drugs, review in detail clinical studies of drug effectiveness, and summarize the advantages and disadvantages of each drug. The third section details specific treatment recommendations for each of the six clinical settings in which treatment of Paget's disease is justified.

Radiological assessment of Paget's disease of bone after treatment with the bisphosphonates EHDP and APD

The effects of therapy on the osteolytic bone lesions of Paget's disease have been assessed from serial bone radiographs. Changes in the rate of progression of lytic "wedge" lesions were measured and alterations in the texture of lytic "blade" lesions were graded on an empirical scale. Useful matching was possible using standard radiographs, although special care was needed to avoid artefacts from suboptimal positioning, magnification and variation in exposure. Serial radiographs were obtained of 57 lytic blade lesions in 54 patients receiving treatment with the bisphosphonate 1-hydroxyethylidene-1, 1-bisphosphonate (EHDP) and of 20 lesions in 20 patients treated with oral or intravenous 3-amino-1-hydroxypropylidene-1, 1-bisphosphonate (APD). Treatment with EHDP was associated with a significant deterioration in bone texture in 50% of lytic blade lesions, and with healing in only 20%. Deterioration was accompanied by an increase in local bone pain in 17% of these patients. In contrast, significant healing was observed in 17 of 20 lytic lesions (eight wedge, nine blade) within 6 months of beginning a course of intravenous or oral APD. In four of eight patients the progression of a lytic tibial wedge was arrested and in the remaining four the direction of wedge movement was reversed. In two patients the wedge had almost completely "filled in", making measurement difficult. Bone healing was usually accompanied by pain relief, reduction in skin temperature and rapid suppression of the urine hydroxyproline (uHP) into the normal range. However, in four patients who received intravenous APD, repair of lytic bone lesions was observed despite persisting elevation of uHP. These improvements with APD were sustained at 12 months, although in one patient whose biochemical indices were restored to normal the resorption front showed further progression, despite initial temporary reversal. The trends apparent in these short-term studies were also seen in four patients in whom wedge velocities were measured over periods of 6-10 years. These results confirm that after treatment of Paget's disease, bone healing or deterioration can be accurately assessed from serial standard radiographs. Reproducible matching is best achieved by ensuring that all radiographs are taken by the same radiographer. Minor alterations in radiological bone texture provide an important index of drug effect which is not always apparent from measurement of biochemical and other indices.

Radiological demonstration of healing in Paget's disease of bone treated with APD

Twenty-three patients with Paget's disease received the bisphosphonate APD and were examined radiologically every 6 months. Because routine roentgenographic procedures were followed, a number of the X rays were not fit for comparison. The radiographic technique, as well as the positioning of the patients, is critical since both could lead to artefacts. All patients reached normal biochemical levels, usually within 6 months. Out of the 23 patients 11 showed definite radiological improvement in one or more lesions; probable improvement was seen in another three. Of the 65 individual lesions, with films that were comparable, 30% definitely and 20% probably improved; 50% did not change but deterioration was never encountered. Osteolytic lesions in the long bones are most suitable for the evaluation of radiological changes and follow-up of these lesions during treatment should be most rewarding.

Osteolytic Paget's bone disease in a young man. Rapid healing with human calcitonin therapy

Paget's bone disease is rare in young adults. Severe osteolytic Paget's bone disease in a 28-year-old man was found to respond, clinically, biochemically, and radiographically, within one month to daily subcutaneous injections of 0.5 mg of synthetic human calcitonin. After two years of therapy, he remains asymptomatic and has no biochemical evidence of Paget's bone disease while receiving injections three times a week. Despite aggressive disease, young patients may rapidly demonstrate the same beneficial response to synthetic human calcitonin therapy as has been observed in middle-aged or elderly patients with Paget's bone disease.

Long-term measurement of skeletal and lean body mass in Paget's disease of bone treated with synthetic human calcitonin

Total body calcium (an index of skeletal mass), ulnar bone density, and total body potassium (lean body mass) were followed for up to 5 years in 38 patients with Paget's disease during treatment with synthetic human calcitonin. Calcium was measured by neutron activation, ulnar density by X-ray photodensitometry, and potassium by counting its natural 40K radioactivity. There was a significant rise in total skeletal mass in a group of 8 patients in the 12 months following the start of therapy, but overall, total bone mass and ulnar density remained constant during treatment. Small mean losses of body potassium were observed (approximately 4%) after several years elapsed on treatment. Over an average period of 12 months after discontinuation of therapy in 21 patients there was no significant mean change in calcium or potassium. The means of the ratios of total body calcium divided by predicted normal calcium (over the whole period of measurement) were 1.08 (males) and 0.99 (females) and were not significantly different. Comparison of the ulnar densities of patients and normal subjects gave similar results. The average ratio of measured to predicted normal potassium was 1.13 (both males and females). Thus there was no indication of depletion in skeletal mass below normal either in the untreated disease or resulting from treatment.

Bone scintigraphy in Paget's disease treated with combined calcitonin and diphosphonate (EHDP)

Bone scintigraphic results for 28 patients with Paget's disease treated with a combination of EHDP and calcitonin are reported. The uptake of the bone scintigraphic agent decreased considerably during the first year of treatment. There was good correlation between scintigraphic and biochemical changes, but most of the 22 patients who attained normal biochemical values still had one or more active lesions scintigraphically. Remission of disease does not therefore mean normalization of the bone scintigram. All affected bones showed a distinct drop in activity, but lesions with a higher initial activity remained more active than lesions with a lower initial activity. One third of the affected bones normalized completely, although radiographic anomalies persisted. There were slight differences in scintigraphic activity depending on the anatomical site. The success of treatment, however, could not be predicted from the pretreatment scintigram. A recurrence of disease was often visible on the scintigram, in certain cases 6 months prior to the biochemical decline. This could be of importance in the therapeutic management of the recurrence.

An unusual morphologic evolution of Paget's disease of bone

A patient with early Paget's disease of bone was treated for 12 months with calcitonin and 10 months with etidronate. During this time the cortex of each diseased bone showed a progressive 2- to 3-fold increase in thickness. Lytic areas regressed and the new bone appeared radiographically very compact. No bowing deformity developed in 3 years of observation. This form of morphologic evolution differs markedly from those previously reported during treatment. For this patient, treatment was instituted very early during the course of the disease and moderately high doses of vitamin D were given during part of the treatment course. Observation of a larger number of patients will be needed to determine whether these factors actually modified the treatment outcome.

Radiologic observations on bone resorption in Paget's disease

The diagnosis of Paget's disease of bone at its earliest osteolytic phase is difficult and requires radiographs of the highest quality. Calcitonin controls the bone resorption of uncomplicated Paget's disease but does not prevent disuse osteoporosis in normal and pagetic bones. Cessation of treatment leads to a recurrence of the osteolytic phase of the disease in some patients. Retreatment with human calcitonin arrests the bone resorption and permits bony consolidation of resorption clefts.

Long-term therapy of Paget's disease of bone with EHDP

Forty patients with Paget's disease of bone were treated with intermittent courses of the diphosphonate, EHDP. Seven individuals had prolonged remissions after their initial course of therapy, nineteen responded to retreatment with 5 mg/kg of EHDP for 6 months of each year, while 14 patients required cycles of 20 mg/kg for 1 month of every 4. Improvement was indicated by alleviation of symptoms and reduction in serum alkaline phosphatase and urinary hydroxyproline. Data suggesting a possible role for parathyroid hormone in the expression of Paget's disease are also discussed.

Treatment of Paget's disease with the calcitonins

Calcitonin has been used in the treatment of Paget's Disease of bone because of its ability to inhibit osteoclastic bone resorption. This results in a return of bone turnover towards normal, as reflected by urinary hydroxyproline and serum alkaline phosphatase. A plateau is reached with these parameters, at about 50% of the pre-treatment level. The cause of this plateau is unknown, but does not indicate resistance to treatment, since it occurs with all forms of calcitonin. Most treated patients experience pain relief, and there is radiological and histological evidence of arrested progression of Paget's Disease in patients treated with calcitonin. Both primary and secondary resistance to calcitonin occur with all calcitonins, including homologous hormone. Antibodies develop commonly in patients treated with pig or salmon calcitonin, but antibody-based clinical resistance has been demonstrated only in a few patients. Methods of selection of patients for treatment and of assessment of response are discussed, and treatment schedules summarized.

Paget's disease and the nervous system

Paget's disease usually is found in patients past the age of 40. Early presenting symptoms include headache, deafness, tinnitus, and pain due to radicular compression. The diagnosis is confirmed by radiographic features and elevated levels of serum alkaline phosphatase and urinary hydroxyproline. Bony overgrowth results in pressure on nearby soft tissues such as the brain, spinal cord, and certain peripheral nerves. The abnormally soft quality of the calvarial bone permits distortion by the weight of the brain. Dorsal inclination of the plane of the foramen magnum and the projection of the odontoid process into the posterior fossa lead to stretching of the brain stem over the odontoid process and the ventral margin of the foramen. Obstructive hydrocephalus may result. Sarcoma of the crainial vault may develop in cases of Paget's disease. Once cervicomedullary or spinal compression has occurred, surgical decompression may be necessary. Three drugs--calcitonin, disodium etidronate, and mithramycin--have been used with some benefit in the treatment of Paget's disease.

The therapeutic uses of calcitonin

Calcitonin is a potent hormonal inhibitor of bone resorption. Its major therapeutic effect is in the treatment of Paget's Disease of bone, in which it has been shown to reduce bone pain, lead to radiological and histological improvement in bone, and to restore abnormal biochemistry towards normal. Some patients are resistant to treatment, and in others resistance may develop during treatment. Although antibodies to pig or to salmon calcitonin develop in almost 50 per cent of treated patients it is only very rarely that resistance may be ascribed to antibodies. There are a number of other clinical states of increased resorption in which the value of calcitonin therapy has yet to be established.

Paget's disease. Radiological changes occurring in untreated patients and those on therapy with salmon calcitonin during two years' observation

Radiological observations over two years were made in 23 patients with Paget's disease. Radiological criteria for progression and regression of disease are defined. Fourteen of the patients were treated with salmon calcitonin. Of these treated patients four showed regression of the disease and only two showed progression, both in the skull vault. Of the remaining nine untreated patients none showed regression but two showed progression. The radiological findings confirm that calcitonin will prevent the extension and sometimes induce healing of Paget's disease in long bones but that the skull appears to respond differently. Radiological changes were slow to occur and yearly or two yearly follow up is sufficient.

A comparison of radiography and radioisotope scanning in the detection of Paget's disease and in the assessment of response to human calcitonin

In eight patients with symptomatic Paget's disease, radiographs and radioisotope bone scans have been compared before treatment by high dose synthetic human calcitonin (CIBA 47175-Ba) and three months and 12 months later. In six patients quantitative radioisotope scans allowed calculation of relative radioactivity in normal bone, Paget's disease and bone adjacent to osteoarthritic joints. Comparison of radiographs and scans showed 69 sites diagnosed as Paget's disease on both examinations; nine sites showed radiographic changes of Paget's disease but had negative radioisotope scans and two sites were abnormal on the scan but radiologically normal. One of these two reverted towards normal during treatment with calcitonin. Comparison of analogue scans done at three months and 12 months with initial scans showed diminished uptake in Paget's disease compared with normal bone, and quantitation showed this was due to decreased absolute uptake in Paget's disease and a slight increase in normal bone. Osteoarthritic bone showed no significant response to calcitonin.

Skeletal turnover and total body elemental composition during extended calcitonin treatment of Paget's disease

Twenty patients with generalized symptomatic Paget's disease had serial measurements of radiocalcium turnover and/or total body elemental composition by in vivo neutron activation analysis during long-term calcitonin therapy. Despite maintained clinical improvement, seven of 15 patients showed partial or total loss of the initial decelerating effect of calcitonin on skeletal turnover, whereas the remaining eight patients maintained the calcitonin-induced deceleration. The changes in skeletal turnover were roughly proportional to the induced changes in serum alkaline phosphatase and urinary hydroxyproline. However, disparities in the magnitude of the changes among the three parameters were not uncommon. Total body calcium was increased by a mean of 22% above predicted prior to calcitonin and decreased significantly by 4% during long-term calcitonin treatment. Total body phosphorus, nitrogen, and sodium also decreased. The phosphorus and sodium losses appeared to be mostly from the skeleton. These data confirm histologic evidence of the disappearance of pagetic bone, resumption of normal lamelar bone formation, and radiographic evidence of a decrease in bone volume during calcitonin treatment and incidate the relative magnitude of this effect. The action of calcitonin in this regard possibly represents a specific effect on Paget's disease beyond its general skeletal effect of reduce cellular activity.